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US20150270410A1. Module fabrication of solar cells with low resistivity electrodes. Google Patents

Publication number US20150270410A1 US20150270410A1 US14/510,008 US201414510008A US2015270410A1 US 20150270410 A1 US20150270410 A1 US 20150270410A1 US 201414510008 A US201414510008 A US 201414510008A US 2015270410 A1 US2015270410 A1 US 2015270410A1 Authority US United States Prior art keywords solar cell solar busbar edge solar cells Prior art date 2013-01-11 Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Granted Application number US14/510,008 Other versions US9412884B2 ( en Inventor Jiunn Benjamin Heng Jianming Fu Zheng Xu Bobby Yang Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) Tesla Inc Original Assignee SolarCity Corp Silevo LLC Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) 2013-01-11 Filing date 2014-10-08 Publication date 2015-09-24 Priority claimed from US201361751733P external-priority 2014-01-13 Priority claimed from US14/153,608 external-priority patent/US9219174B2/en 2014-10-08 Application filed by SolarCity Corp, Silevo LLC filed Critical SolarCity Corp 2014-10-08 Priority to US14/510,008 priority Critical patent/US9412884B2/en 2014-10-23 Assigned to SILEVO, INC. reassignment SILEVO, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FU, JIANMING, XU, ZHENG, HENG, JIUNN BENJAMIN, YANG, BOBBY 2014-12-08 Priority to US14/563,867 priority patent/US10074755B2/en 2015-01-09 Priority to CN201580003510.7A priority patent/CN105874609B/en 2015-01-09 Priority to PCT/US2015/010913 priority patent/WO2015106167A2/en 2015-01-09 Priority to PCT/US2015/010916 priority patent/WO2015106170A2/en 2015-01-09 Priority to JP2016544849A priority patent/JP6220979B2/en 2015-01-09 Priority to KR1020167017439A priority patent/KR101841865B1/en 2015-01-09 Priority to EP15701288.1A priority patent/EP3095139B1/en 2015-01-09 Priority to CN201580003511.1A priority patent/CN105917472B/en 2015-01-09 Priority to MX2016008742A priority patent/MX359188B/en 2015-01-09 Priority to EP15701287.3A priority patent/EP3095138B1/en 2015-01-13 Priority to CN201520964549.2U priority patent/CN205376541U/en 2015-01-13 Priority to CN201520023788.8U priority patent/CN204538036U/en 2015-01-13 Priority to CN201520022485.4U priority patent/CN204885178U/en 2015-05-04 Assigned to SOLARCITY CORPORATION reassignment SOLARCITY CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SILEVO LLC 2015-09-24 Publication of US20150270410A1 publication Critical patent/US20150270410A1/en 2016-01-22 Assigned to SILEVO, LLC reassignment SILEVO, LLC MERGER AND CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: SILEVO, INC., SUNFLOWER ACQUISITION LLC 2016-07-27 Priority to US15/221,200 priority patent/US10115839B2/en 2016-08-09 Publication of US9412884B2 publication Critical patent/US9412884B2/en 2016-08-09 Application granted granted Critical 2021-05-06 Assigned to TESLA, INC. reassignment TESLA, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SOLARCITY CORPORATION Status Active legal-status Critical Current 2034-01-29 Adjusted expiration legal-status Critical

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H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/04 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
H01L31/042 — PV modules or arrays of single PV cells
H01L31/05 — Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
H01L31/0504 — Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/02 — Details
H01L31/02002 — Arrangements for conducting electric current to or from the device in operations
H01L31/02005 — Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier
H01L31/02008 — Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier for solar cells or solar cell modules
H01L31/0201 — Arrangements for conducting electric current to or from the device in operations for device characterised by at least one potential jump barrier or surface barrier for solar cells or solar cell modules comprising specially adapted module bus-bar structures

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/02 — Details
H01L31/0224 — Electrodes
H01L31/022408 — Electrodes for devices characterised by at least one potential jump barrier or surface barrier
H01L31/022425 — Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
H01L31/022441 — Electrode arrangements specially adapted for back-contact solar cells

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/0248 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
H01L31/0352 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
H01L31/035209 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/04 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
H01L31/042 — PV modules or arrays of single PV cells

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/04 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
H01L31/06 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
H01L31/068 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
H01L31/0684 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells double emitter cells, e.g. bifacial solar cells

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/04 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
H01L31/06 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
H01L31/072 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
H01L31/0745 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells
H01L31/0747 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer or HIT® solar cells; solar cells

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/18 — Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof

H — ELECTRICITY
H02 — GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
H02S — GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRA-RED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
H02S40/00 — Components or accessories in combination with PV modules, not provided for in groups H02S10/00. H02S30/00
H02S40/30 — Electrical components

H — ELECTRICITY
H02 — GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
H02S — GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRA-RED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
H02S40/00 — Components or accessories in combination with PV modules, not provided for in groups H02S10/00. H02S30/00
H02S40/30 — Electrical components
H02S40/36 — Electrical components characterised by special electrical interconnection means between two or more PV modules, e.g. electrical module-to-module connection

Y — GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02 — TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
Y02E — REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
Y02E10/00 — Energy generation through renewable energy sources
Y02E10/50 — Photovoltaic [PV] energy
Y02E10/547 — Monocrystalline silicon PV cells

Y — GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02 — TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
Y02E — REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
Y02E10/00 — Energy generation through renewable energy sources
Y02E10/50 — Photovoltaic [PV] energy
Y02E10/56 — Power conversion systems, e.g. maximum power point trackers

Abstract

One embodiment of the present invention provides a solar module. The solar module includes a front-side cover, a back-side cover, and a plurality of solar cells situated between the front- and back-side covers. A respective solar cell includes a multi-layer semiconductor structure, a front-side electrode situated above the multi-layer semiconductor structure, and a back-side electrode situated below the multi-layer semiconductor structure. Each of the front-side and the back-side electrodes comprises a metal grid. A respective metal grid comprises a plurality of finger lines and a single busbar coupled to the finger lines. The single busbar is configured to collect current from the finger lines.

Description

This application is a continuation-in-part application of U.S. patent application Ser. No. 14/153,608 (attorney docket number SSP13-1001US), entitled “MODULE FABRICATION OF SOLAR CELLS WITH LOW RESISTIVITY ELECTRODES,” by inventors Jiunn Benjamin Heng, Jianming Fu, Zheng Xu, and Bobby Yang, filed 13 Jan. 2014, which claims the benefit of U.S. Provisional Application No. 61/751,733, Attorney Docket Number SSP13-1001PSP, entitled “Module Fabrication Using Bifacial Tunneling Junction Solar Cells with Copper Electrodes,” by inventors Jiunn Benjamin Heng, Jianming Fu, Zheng Xu, and Bobby Yang, filed 11 Jan. 2013.

This disclosure is generally related to the fabrication of solar cells. specifically, this disclosure is related to module fabrication of bifacial tunneling junction solar cells.

The negative environmental impact of fossil fuels and their rising cost have resulted in a dire need for cleaner, cheaper alternative energy sources. Among different forms of alternative energy sources, solar power has been favored for its cleanness and wide availability.

A solar cell converts light into electricity using the photovoltaic effect. There are several basic solar cell structures, including a single p-n junction, p-i-n/n-i-p, and multi-junction. A typical single p-n junction structure includes a p-type doped layer and an n-type doped layer. Solar cells with a single p-n junction can be homojunction solar cells or heterojunction solar cells. If both the p-doped and n-doped layers are made of similar materials (materials with equal Band gaps), the solar cell is called a homojunction solar cell. In contrast, a heterojunction solar cell includes at least two layers of materials of different bandgaps. A p-i-n/n-i-p structure includes a p-type doped layer, an n-type doped layer, and an intrinsic (undoped) semiconductor layer (the i-layer) sandwiched between the p-layer and the n-layer. A multi-junction structure includes multiple single-junction structures of different bandgaps stacked on top of one another.

In a solar cell, light is absorbed near the p-n junction generating carriers. The carriers diffuse into the p-n junction and are separated by the built-in electric field, thus producing an electrical current across the device and external circuitry. An important metric in determining a solar cell’s quality is its energy-conversion efficiency, which is defined as the ratio between power converted (from absorbed light to electrical energy) and power collected when the solar cell is connected to an electrical circuit.

FIG. 1 presents a diagram illustrating an exemplary solar cell (prior art). Solar cell 100 includes an n-type doped Si substrate 102, a p silicon emitter layer 104, a front electrode grid 106, and an Al back electrode 108. Arrows in FIG. 1 indicate incident sunlight. As one can see from FIG. 1. Al back electrode 108 covers the entire backside of solar cell 100, hence preventing light absorption at the backside. over, front electrode grid 106 often includes a metal grid that is opaque to sunlight, and casts a shadow on the front surface of solar cell 100. For a conventional solar cell, the front electrode grid can block up to 8% of the incident sunlight, thus significantly reducing the conversion efficiency.

One embodiment of the present invention provides a solar module. The solar module includes a front-side cover, a back-side cover, and a plurality of solar cells situated between the front- and back-side covers. A respective solar cell includes a multi-layer semiconductor structure, a front-side electrode situated above the multi-layer semiconductor structure, and a back-side electrode situated below the multi-layer semiconductor structure. Each of the front-side and the back-side electrodes comprises a metal grid. A respective metal grid comprises a plurality of finger lines and a single busbar coupled to the finger lines. The single busbar is configured to collect current from the finger lines.

In a variation on the embodiment, the single busbar is located at a center of a respective surface of the solar cell.

In a further variation, two adjacent solar cells are strung together by a stringing ribbon woven from a front surface of a solar cell to a back surface of an adjacent solar cell. The stringing ribbon is soldered to single busbars on the front and the back surfaces, and a width of the stringing ribbon is substantially similar to a width of the single busbar.

In a variation on the embodiment, single busbars of a front and a back surface of the solar cell are located at opposite edges.

In a further variation, two adjacent solar cells are coupled together by a metal tab soldered to a first single busbar at an edge of a solar cell and a second single busbar at an adjacent edge of the adjacent solar cell. A width of the metal tab is substantially similar to a length of the first and the second single busbar.

In a further variation, the first single busbar is on the front surface of the solar cell, and the second single busbar is on the back surface of the adjacent solar cell.

In a further variation, the first single busbar and the second single busbar are on the same side of surface of the two solar cells.

In a further variation, a plurality of solar cells are coupled by metal tabs into a string, and wherein a plurality of strings are coupled electrically in series or in parallel

In a further variation, two adjacent solar cells are coupled together by overlapping edges of the two adjacent solar cells. The edges of the two adjacent solar cells are overlapped in such a way that a top edge busbar of a first solar cell is coupled to a bottom edge busbar of a second adjacent solar cell, thereby facilitating a serial electrical connection between the two adjacent solar cells.

In a further variation, a plurality of solar cells are coupled by overlapping edges to form a string, and wherein a plurality of strings are coupled electrically in series or in parallel.

In a variation on the embodiment, the multi-layer semiconductor structure includes a base layer, a front- or back-side emitter, and a back or front surface field layer.

In a further variation, the multi-layer semiconductor structure further includes a quantum tunneling barrier (QTB) layer situated at both sides of the base layer.

In a variation on the embodiment, the solar module further includes a plurality of maximum power point tracking (MPPT) devices. A respective MPPT device is coupled to an individual solar cell, thereby facilitating cell-level MPPT.

In a further variation, the solar module further includes a plurality of MPPT devices, wherein a respective MPPT device is coupled to a string of solar cells, thereby facilitating string-level MPPT.

In a variation on the embodiment, the front-side and the back-side covers are transparent to facilitate bifacial configuration of the solar module.

In a variation on the embodiment, the plurality of solar cells includes at least one of: a 5-inch solar cell, a 6-inch solar cell, and a ⅛, ⅙, ¼, ⅓, or ½ of a 5-inch or a 6-inch solar cell.

One embodiment of the present invention provides a solar cell coupling system. The system includes a first solar cell and a second solar cell. A respective solar cell comprises a front-side electrode and a back-side electrode. A respective electrode comprises a plurality of finger lines and a single busbar coupled to the finger lines, the bus bar being situated at the edge of the respective solar cell. The system further includes a metal tab coupling the front-side electrode of the first solar cell and the back-side electrode of the second solar cell.

One embodiment of the present invention provides a solar cell coupling system. The system includes a first solar cell and a second solar cell. A respective solar cell comprises a front-side electrode and a back-side electrode. A respective electrode comprises a plurality of finger lines and a single busbar coupled to the finger lines, the bus bar being situated at the edge of the respective solar cell. An edge of the first solar cell overlaps with an edge of the second solar cell such that the busbar of the front-side electrode of the first solar cell is coupled to the busbar of the back-side electrode of the second solar cell.

FIG. 2 presents a diagram illustrating an exemplary double-sided tunneling junction solar cell, in accordance with an embodiment of the present invention.

FIG. 3C presents a diagram illustrating a cross-sectional view of the bifacial solar cell with a single center busbar per surface, in accordance with an embodiment of the present invention.

FIG. 3D presents a diagram illustrating the front surface of an exemplary bifacial solar cell, in accordance with an embodiment of the present invention.

FIG. 3E presents a diagram illustrating the back surface of an exemplary bifacial solar cell, in accordance with an embodiment of the present invention.

FIG. 3F presents a diagram illustrating a cross-sectional view of the bifacial solar cell with a single edge busbar per surface, in accordance with an embodiment of the present invention.

FIG. 4 presents a diagram illustrating the percentage of power loss as a function of the gridline (finger) length for different aspect ratios.

FIG. 5A presents a diagram illustrating a typical solar panel that includes a plurality of conventional double-busbar solar cells (prior art).

FIG. 5C presents a diagram illustrating the serial connection between two adjacent solar cells with a single edge busbar per surface, in accordance with an embodiment of the present invention.

FIG. 5D presents a diagram illustrating a string of solar cells with front-side electrodes of adjacent cells having the same polarity, in accordance with an embodiment of the present invention.

FIG. 5E presents a diagram illustrating a string of solar cells with front-side electrodes of adjacent cells having opposite polarities, in accordance with an embodiment of the present invention.

FIG. 5F presents a diagram illustrating the serial connection between two adjacent solar cells with a single edge busbar per surface, in accordance with an embodiment of the present invention.

FIG. 5G presents a diagram illustrating the side-view of a string of adjacent edge-overlapped solar cells, in accordance with an embodiment of the present invention.

FIG. 5H presents a diagram illustrating the top-view of two adjacent edge-overlapped solar cells, in accordance with an embodiment of the present invention.

FIG. 5I presents a diagram illustrating the bottom-view of two adjacent edge-overlapped solar cells, in accordance with an embodiment of the present invention

FIG. 5J presents a diagram illustrating an exemplary solar panel that includes a plurality of solar cells with a single busbar at the edge, in accordance with an embodiment of the present invention.

FIG. 6A presents a diagram illustrating the percentages of the ribbon-resistance-based power loss for the double busbar (DBB) and the single busbar (SBB) configurations for different types of cells, different ribbon thicknesses, and different panel configurations.

FIG. 6B presents a diagram comparing the power loss difference between the stringing ribbons and the single tab for different ribbon/tab thicknesses.

FIG. 7C presents a diagram illustrating one exemplary placement of maximum power point tracking (MPPT) integrated circuit (IC) chips in a solar panel with single-edge-busbar solar cells, in accordance with an embodiment of the present invention.

FIG. 7D presents a diagram illustrating the cross-sectional view of an exemplary solar module implementing cell-level MPPT, in accordance with an embodiment of the present invention.

FIG. 8 presents a flow chart illustrating the process of fabricating a solar cell module, in accordance with an embodiment of the present invention.

The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Embodiments of the present invention provide a high-efficiency solar module. The solar module includes a bifacial tunneling junction solar cell with electroplated Cu gridlines serving as front- and back-side electrodes. To reduce shading and cost, a single Cu busbar or tab is used to collect current from the Cu fingers. In some embodiments, the single busbar or tab is placed in the center of the front and backsides of the solar cell. To further reduce shading, in some embodiments, the single Cu busbar or tab is placed on the opposite edges of the front and backside of a solar cell. Both the fingers and the busbars can be fabricated using a technology for producing shade-free electrodes. In addition, the fingers and busbars can include high-aspect ratio Cu gridlines to ensure low resistivity. When multiple solar cells are stringed or tabbed together to form a solar panel, conventional stringing/tabbing processes are modified based on the locations of the busbars. Compared with conventional solar modules based on monofacial, double-busbar solar cells, embodiments of the present invention provide solar modules with up to an 18% gain in power. over, 30% of the power that may be lost due to a partially shaded solar panel can be recouped by applying maximum power point tracking (MPPT) technology at the cell level. In some embodiments, each solar cell within a solar panel is coupled to an MPPT integrated circuit (IC) chip.

FIG. 2 presents a diagram illustrating an exemplary double-sided tunneling junction solar cell, in accordance with an embodiment of the present invention. Double-sided tunneling junction solar cell 200 includes a substrate 202, quantum tunneling barrier (QTB) layers 204 and 206 covering both surfaces of substrate 202 and passivating the surface-defect states, a front-side doped a-Si layer forming a front emitter 208, a back-side doped a-Si layer forming a BSF layer 210, a front transparent conducting oxide (TCO) layer 212, a back TCO layer 214, a front metal grid 216, and a back metal grid 218. Note that it is also possible to have the emitter layer at the backside and a front surface field (FSF) layer at the front side of the solar cell. Details, including fabrication methods, about double-sided tunneling junction solar cell 200 can be found in U.S. patent application Ser. No. 12/945,792 (Attorney Docket No. SSP10-1002US), entitled “Solar Cell with Oxide Tunneling Junctions,” by inventors Jiunn Benjamin Heng, Chentao Yu, Zheng Xu, and Jianming Fu, filed 12 Nov. 2010, the disclosure of which is incorporated by reference in its entirety herein.

As one can see from FIG. 2. the symmetric structure of double-sided tunneling junction solar cell 200 ensures that double-sided tunneling junction solar cell 200 can be bifacial given that the backside is exposed to light. In solar cells, the metallic contacts, such as front and back metal grids 216 and 218, are necessary to collect the current generated by the solar cell. In general, a metal grid includes two types of metal lines, including busbars and fingers. specifically, busbars are wider metal strips that are connected directly to external leads (such as metal tabs), while fingers are finer areas of metalization which collect current for delivery to the busbars. The key design trade-off in the metal grid design is the balance between the increased resistive losses associated with a widely spaced grid and the increased reflection and shading effect caused by a high fraction of metal coverage of the surface. In conventional solar cells, to prevent power loss due to series resistance of the fingers, at least two busbars are placed on the surface of the solar cell to collect current from the fingers, as shown in FIG. 3A. For standardized 5-inch solar cells (which can be 5×5 inch 2 squares or pseudo squares with rounded corners), typically there are two busbars at each surface. For larger, 6-inch solar cells (which can be 5×5 inch 2 squares or pseudo squares with rounded corners), three or more busbars may be needed depending on the resistivity of the electrode materials. Note that in FIG. 3A a surface (which can be the front or back surface) of solar cell 300 includes a plurality of parallel finger lines, such as finger lines 302 and 304; and two busbars 306 and 308 placed perpendicular to the finger lines. Note that the busbars are placed in such a way as to ensure that the distance (and hence the resistance) from any point on a finger to a busbar is small enough to minimize power loss. However, these two busbars and the metal ribbons that are later soldered onto these busbars for inter-cell connections can create a significant amount of shading, which degrades the solar cell performance.

In some embodiments of the present invention, the front and back metal grids, such as the finger lines, can include electroplated Cu lines, which have reduced resistance compared with conventional Ag grids. For example, using an electroplating or electroless plating technique, one can obtain Cu grid lines with a resistivity of equal to or less than 5×10 −6 Ω·cm. Details about an electroplated Cu grid can be found in U.S. patent application Ser. No. 12/835,670 (Attorney Docket No. SSP10-1001US), entitled “Solar Cell with Metal Grid Fabricated by Electroplating,” by inventors Jianming Fu, Zheng Xu, Chentao Yu, and Jiunn Benjamin Heng, filed 13 Jul. 2010; and U.S. patent application Ser. No. 13/220,532 (Attorney Docket No. SSP10-1010US), entitled “Solar Cell with Electroplated Metal Grid,” by inventors Jianming Fu, Jiunn Benjamin Heng, Zheng Xu, and Chentao Yu, filed 29 Aug. 2011, the disclosures of which are incorporated by reference in their entirety herein.

The reduced resistance of the Cu fingers makes it possible to have a metal grid design that maximizes the overall solar cell efficiency by reducing the number of busbars on the solar cell surface. In some embodiments of the present invention, a single busbar is used to collect finger current. The power loss caused by the increased distance from the fingers to the busbar can be balanced by the reduced shading.

FIG. 3B presents a diagram illustrating the front or back surface of an exemplary bifacial solar cell with a single center busbar per surface, in accordance with an embodiment of the present invention. In FIG. 3B. the front or back surface of a solar cell 310 includes a single busbar 312 and a number of finger lines, such as finger lines 314 and 316. FIG. 3C presents a diagram illustrating a cross-sectional view of the bifacial solar cell with a single center busbar per surface, in accordance with an embodiment of the present invention. The semiconductor multilayer structure shown in FIG. 3C can be similar to the one shown in FIG. 2. Note that the finger lines are not shown in FIG. 3C because the cut plane cuts between two finger lines. In the example shown in FIG. 3C. busbar 312 runs in and out of the paper, and the finger lines run from left to right. As discussed previously, because there is only one busbar at each surface, the distances from the edges of the fingers to the busbar are longer. However, the elimination of one busbar reduces shading, which not only compensates for the power loss caused by the increased finger-to-busbar distance, but also provides additional power gain. For a standard sized solar cell, replacing two busbars with a single busbar in the center of the cell can produce a 1.8% power gain.

FIG. 3D presents a diagram illustrating the front surface of an exemplary bifacial solar cell, in accordance with an embodiment of the present invention. In FIG. 3D. the front surface of solar cell 320 includes a number of horizontal finger lines and a vertical single busbar 322, which is placed at the right edge of solar cell 320. specifically, busbar 322 is in contact with the rightmost edge of all the finger lines, and collects current from all the finger lines. FIG. 3E presents a diagram illustrating the back surface of an exemplary bifacial solar cell, in accordance with an embodiment of the present invention. In FIG. 3E. the back surface of solar cell 320 includes a number of horizontal finger lines and a vertical single busbar 324, which is placed at the left edge of solar cell 320. Similar to busbar 322, single busbar 324 is in contact with the leftmost edge of all the finger lines. FIG. 3F presents a diagram illustrating a cross-sectional view of the bifacial solar cell with a single edge busbar per surface, in accordance with an embodiment of the present invention. The semiconductor multilayer structure shown in FIG. 3F can be similar to the one shown in FIG. 2. Like FIG. 3C. in FIG. 3F. the finger lines (not shown) run from left to right, and the busbars run in and out of the paper. From FIGS. 3D-3F. one can see that in this embodiment, the busbars on the front and the back surfaces of the bifacial solar cell are placed at the opposite edges of the cell. This configuration can further improve power gain because the busbar-induced shading now occurs at locations that were less effective in energy production. In general, the edge-busbar configuration can provide at least a 2.1% power gain.

Note that the single busbar per surface configurations (either the center busbar or the edge busbar) not only can provide power gain, but also can reduce fabrication cost, because less metal will be needed for busing ribbons. over, in some embodiments of the present invention, the metal grid on the front sun-facing surface can include parallel metal lines (such as fingers), each having a cross-section with a curved parameter to ensure that incident sunlight on these metal lines is reflected onto the front surface of the solar cell, thus further reducing shading. Such a shade-free front electrode can be achieved by electroplating Ag- or Sn-coated Cu using a well-controlled, cost-effective patterning scheme.

It is also possible to reduce the power-loss effect caused by the increased distance from the finger edges to the busbars by increasing the aspect ratio of the finger lines. FIG. 4 presents a diagram illustrating the percentage of power loss as a function of the gridline (finger) length for different aspect ratios. In the example shown in FIG. 4. the gridlines (or fingers) are assumed to have a width of 60 μm. As one can see from FIG. 4. for gridlines with an aspect ratio of 0.5, the power loss degrades from 3.6% to 7.5% as the gridline length increases from 30 mm to 100 mm. However, with a higher aspect ratio, such as 1.5, the power loss degrades from 3.3% to 4.9% for the same increase of gridline length. In other words, using high-aspect ratio gridlines can further improve solar cell/module performance. Such high-aspect ratio gridlines can be achieved using an electroplating technique. Details about the shade-free electrodes with high-aspect ratio can be found in U.S. patent application Ser. No. 13/048,804 (Attorney Docket No. SSP10-1003US), entitled “Solar Cell with a Shade-Free Front Electrode,” by inventors Zheng Xu, Jianming Fu, Jiunn Benjamin Heng, and Chentao Yu, filed 15 Mar. 2011, the disclosure of which is incorporated by reference in its entirety herein.

Multiple solar cells with a single busbar (either at the cell center or the cell edge) per surface can be assembled to form a solar module or panel via a typical panel fabrication process with minor modifications. Based on the locations of the busbars, different modifications to the stringing/tabbing process are needed. In conventional solar module fabrications, the double-busbar solar cells are strung together using two stringing ribbons (also called tabbing ribbons) which are soldered onto the busbars. specifically, the stringing ribbons weave from the front surface of one cell to the back surface of the adjacent cell to connect the cells in series. For the single busbar in the cell center configuration, the stringing process is very similar, except that only one stringing ribbon is needed to weave from the front surface of one cell to the back surface of the other.

FIG. 5A presents a diagram illustrating a typical solar panel that includes a plurality of conventional double-busbar solar cells (prior art). In FIG. 5A. solar panel 500 includes a 6×12 array (with 6 rows and 12 cells in a row) of solar cells. Adjacent solar cells in a row are connected in series to each other via two stringing ribbons, such as a stringing ribbon 502 and a stringing ribbon 504. specifically, the stringing ribbons connect the top electrodes of a solar cell to the bottom electrodes of the next solar cell. At the end of each row, the stringing ribbons join together with stringing ribbons from the next row by a wider bus ribbon, such as a bus ribbon 506. In the example shown in FIG. 5A. the rows are connected in series with two adjacent rows being connected to each other at one end. Alternatively, the rows can connect to each other in a parallel fashion with adjacent rows being connected to each other at both ends. Note that FIG. 5A illustrates only the top side of the solar panel; the bottom side of the solar panel can be very similar due to the bifacial characteristics of the solar cells. For simplicity, the fingers, which run perpendicular to the direction of the solar cell row (and hence the stringing ribbons), are not shown in FIG. 5A.

FIG. 5B presents a diagram illustrating an exemplary solar panel that includes a plurality of solar cells with a single busbar at the center, in accordance with an embodiment of the present invention. In FIG. 5B. solar panel 510 includes a 6×12 array of solar cells. Adjacent solar cells in a row are connected in series to each other via a single stringing ribbon, such as a ribbon 512. As in solar panel 500, the single stringing ribbons at the ends of adjacent rows are joined together by a wider bus ribbon, such as a bus ribbon 514. Because only one stringing ribbon is necessary to connect adjacent cells, compared with solar panel 500 in FIG. 5A. the total length of the bus ribbon used in fabricating solar panel 510 can be significantly reduced. For six-inch cells, the length of the single stringing ribbon that connects two adjacent cells can be around 31 cm, compared with 62 cm of stringing ribbons needed for the double-busbar configuration. Note that such a length reduction can further reduce series resistance and fabrication cost. Similar to FIG. 5A. in FIG. 5B. the rows are connected in series. In practice, the solar cell rows can be connected in parallel as well. Also like FIG. 5A. the finger lines run perpendicular to the direction of the solar cell row (and hence the stringing ribbons) and are not shown in FIG. 5B.

Comparing FIG. 5B with FIG. 5A. one can see that only a minor change is needed in the stringing/tabbing process to assemble solar cells with a single center busbar into a solar panel. However, for solar cells with a single edge busbar per surface, more changes may be needed. FIG. 5C presents a diagram illustrating the serial connection between two adjacent solar cells with a single edge busbar per surface, in accordance with an embodiment of the present invention. In FIG. 5C. solar cell 520 and solar cell 522 are coupled to each other via a single tab 524. specifically, one end of single tab 524 is soldered to the edge busbar located on the front surface of solar cell 520, and the other end of single tab 524 is soldered to the edge busbar located on the back surface of solar cell 522, thus connecting solar cells 520 and 522 in series. From FIG. 5C. one can see that the width of single tab 524 is along the length of the edge busbars (in the direction that is vertical to the finger lines) and is substantially the same as the length of the edge busbars, and the ends of single tab 524 are soldered to the edge busbars along their length. In some embodiments, the width of single tab 524 can be between 12 and 16 cm. On the other hand, the length of single tab 524 is determined by the packing density or the distance between adjacent solar cells, and can be quite short. In some embodiments, the length of single tab 524 can be between 3 and 12 mm. In further embodiments, the length of single tab 524 can be between 3 and 5 mm. This geometric configuration (a wider width and a shorter length) ensures that single tab 524 has a very low series resistance. The finger lines, such as a finger line 526, run in a direction along the length of single tab 524. Note that this is different from the conventional two-busbar configuration and the single center-busbar configuration where the fingers are perpendicular to the stringing ribbons connecting two adjacent solar cells. Hence, the conventional, standard stringing process needs to be modified by rotating each cell 90 degrees in order to string two solar cells together as shown in FIG. 5C.

Note that the edge busbar configuration works well with an edge tab going from the front edge of one solar cell to the back edge of an adjacent solar cell, when the front-side electrodes for all the cells are of the same polarity and the back-side electrodes for all the cells are all of opposite polarity. Furthermore, when the front-side electrodes of adjacent cells have different polarities (and, similarly, the back-side electrodes of adjacent cells also have different polarities), the edge tab can couple the front-side edge of one solar cell to the front-side edge of the adjacent solar cell, or the back-side edge of one solar cell to the back-side edge of the adjacent solar cell.

Multiple solar cells can be coupled this way to form a string, and multiple strings can be coupled electrically in series or in parallel. FIG. 5D presents a diagram illustrating a string of solar cells with front-side electrodes of adjacent cells having the same polarity, in accordance with an embodiment of the present invention. In FIG. 5D. a string of solar cells (such as cells 511 and 513) are sandwiched between a front glass cover 501 and a back cover 503. specifically, the solar cells are arranged in such a way that allows the front-side electrodes of all the cells to be of one polarity and their back-side electrodes to be of the other polarity. Metal tabs, such as tabs 515 and 517, serially couple adjacent solar cells by coupling together the front edge busbar of a solar cell and the back edge busbar of its adjacent solar cell. In the example shown in FIG. 5D. metal tab 515 couples front edge busbar 507 of solar cell 511 to back edge busbar 509 of solar cell 513.

FIG. 5E presents a diagram illustrating a string of solar cells with front-side electrodes of adjacent cells having opposite polarities, in accordance with an embodiment of the present invention. In FIG. 5E. a string of solar cells (such as cells 521 and 523) are arranged in such a way that allows the front-side electrodes of adjacent cells to have alternating polarities, and similarly, the back-side electrodes of adjacent solar cells can also have alternating polarities. Metal tabs, such as tabs 525 and 527, serially couple adjacent solar cells by coupling two adjacent front edge busbars to each other, and two adjacent back edge busbars to each other. In the example shown in FIG. 5E. metal tab 525 couples front edge busbar 531 of solar cell 521 to front edge busbar 533 (which has a polarity opposite to that of edge busbar 531) of solar cell 523.

In addition to using a single tab to serially connect two adjacent single-busbar solar cells, it is also possible to establish a serial connection between adjacent solar cells by stacking the corresponding edge busbars. FIG. 5F presents a diagram illustrating the serial connection between two adjacent solar cells with a single edge busbar per surface, in accordance with an embodiment of the present invention. In FIG. 5F. solar cell 530 and solar cell 532 are coupled via an edge busbar 534 located at the top surface of solar cell 530 and an edge busbar 536 located at the bottom surface of solar cell 532. specifically, the bottom surface of solar cell 532 partially overlaps the top surface of solar cell 530 at the edge in such a way that bottom edge busbar 536 is placed on top of and in direct contact with top edge busbar 534. In some embodiments, edge busbars 534 and 536 may include a plated (using an electroplating or electroless plating technique) metal stack that includes multiple layers of metals, such as Ni, Cu, Sn, and Ag. Detailed descriptions of the plated metal stack can be found in U.S. patent application Ser. No. 12/835,670 (Attorney Docket No. SSP10-1001US), entitled “Solar Cell with Metal Grid Fabricated by Electroplating,” by inventors Jianming Fu, Zheng Xu, Chentao Yu, and Jiunn Benjamin Heng, filed 13 Jul. 2010; and U.S. patent application Ser. No. 13/220,532 (Attorney Docket No. SSP10-1010US), entitled “Solar Cell with Electroplated Metal Grid,” by inventors Jianming Fu, Jiunn Benjamin Heng, Zheng Xu, and Chentao Yu, filed 29 Aug. 2011, the disclosures of which are incorporated by reference in their entirety herein.

In some embodiments, the edge busbars that are in contact with each other are soldered together to enable a serial electrical connection between adjacent solar cells. In further embodiments, the soldering may happen concurrently with a lamination process, during which the edge-overlapped solar cells are placed in between a front-side cover and a back-side cover along with appropriate sealant material, which can include adhesive polymer, such as ethylene vinyl acetate (EVA). During lamination, heat and pressure are applied to cure the sealant, sealing the solar cells between the front-side and back-side covers. The same heat and pressure can result in the edge busbars that are in contact, such as edge busbars 534 and 536, being soldered together. Note that if the edge busbars include a top Sn layer, there is no need to insert additional soldering or adhesive materials between the top and bottom busbars (such as busbars 534 and 536) of adjacent solar cells. Also note that because the solar cells are five-inch or six-inch Si wafers that are relatively flexible, the pressure used during the lamination process can be relatively large without the worry that the cells may crack under such pressure. In some embodiments, the pressure applied during lamination process can be above 1.0 atmospheres, such as 1.2 atmospheres.

FIG. 5G presents a diagram illustrating the side-view of a string of adjacent edge-overlapped solar cells, in accordance with an embodiment of the present invention. In FIG. 5G. solar cell 540 partially overlaps adjacent solar cell 542, which also partially overlaps (on its opposite end) solar cell 544. Such a string of solar cells forms a pattern that is similar to roof shingles. Note that the overlapping should be kept to a minimum to minimizing shading caused by the overlapping. In some embodiments, the single busbars (both at the top and the bottom surface) are placed at the very edge of the solar cell (as shown in FIG. 5G ), thus minimizing the overlapping.

Because the solar cells are bifacial (meaning that light enters from both top and bottom surfaces of the solar cells), it is desirable to have a symmetrical arrangement at the top and bottom surfaces of the solar cells. FIG. 5H presents a diagram illustrating the top-view of two adjacent edge-overlapped solar cells, in accordance with an embodiment of the present invention. In FIG. 5H. solar cells 550 and 552 partially overlap each other at the right edge of solar cell 550. The top surface (which is the surface in view) of solar cell 550 includes a number of finger lines (such as finger lines 554 and 556) that are parallel to each other and an edge busbar that is vertical to the finger lines. Note that the edge busbar is not shown in FIG. 5H because it is covered by the left edge of solar cell 552. Similarly, the top surface of solar cell 552 includes a number of finger lines (such as finger lines 558 and 560) that are parallel to each other and an edge busbar 562 that is vertical to the finger lines. FIG. 5I presents a diagram illustrating the bottom-view of two adjacent edge-overlapped solar cells, in accordance with an embodiment of the present invention. In FIG. 5I. solar cells 550 and 552 partially overlap each other at the right edge of solar cell 550. The bottom surface (which is the surface in view) of solar cell 550 includes a number of finger lines (such as finger lines 564 and 566) that are parallel to each other and an edge busbar 568 that is vertical to the finger lines. Similarly, the bottom surface of solar cell 552 includes a number of finger lines (such as finger lines 570 and 572) that are parallel to each other and an edge busbar that is vertical to the finger lines. Note that the edge busbar is not shown in FIG. 5I because it is covered by the right edge of solar cell 550. Having the same metal grid at the top and bottom surfaces of the solar cell ensures bifacial functionality.

FIG. 5J presents a diagram illustrating an exemplary solar panel that includes a plurality of solar cells with a single busbar at the edge, in accordance with an embodiment of the present invention. In FIG. 5J. solar panel 580 includes a 6×12 array of solar cells. Solar cells in a row are connected in series to each other either via a single tab, such as a tab 582, or by edge-overlapping in a shingled pattern. At the end of the row, instead of using a wider bus ribbon to connect stringing ribbons from adjacent cells together (like the examples shown in FIGS. 5A and 5B ), here we simply use a tab that is sufficiently wide to extend through edges of both end cells of the adjacent rows. For example, an extra-wide tab 584 extends through edges of cells 586 and 588. For serial connection, extra-wide tab 584 can connect the busbar at the top surface of cell 586 with the busbar at the bottom surface of cell 588, which means solar cells 586 and 588 are placed in such a way that the top edge busbar of cell 586 aligns with the bottom edge busbar of cell 588. Note that if the solar cells in a row are placed in a shingled pattern, the adjacent rows may have opposite shingle patterns, such as right-side on top or left-side on top. For parallel connection, extra-wide tab 584 may connect both the top/bottom busbars of cells 586 and 588. If the solar cells in a row are shingled, the shingle pattern of all rows remains the same. Unlike examples shown in FIGS. 5A and 5B. in FIG. 5I. the finger lines (not shown) run along the direction of the solar cell rows.

The stringing ribbons or tabs can also introduce power loss due to their series resistance. In general, the distributed power loss through series resistance of the stringing ribbons increases with the size of the cell. over, using single stringing ribbon instead of two ribbons also increases this series-resistance-induced power loss because the single-ribbon configuration means that there is more current on each ribbon, and the power loss is proportional to the square of the current. To reduce such a power loss, one needs to reduce the series resistance of the stringing ribbon. For the single center-busbar configuration, the width of the ribbon is determined by the width of the busbar, which can be between 0.5 and 3 mm. Hence, one way to reduce the resistance of the ribbon is to increase its thickness as thicker ribbons have lower resistivity. FIG. 6A presents a diagram illustrating the percentages of the ribbon-resistance-based power loss for the double busbar (DBB) and the single busbar (SBB) configurations for different types of cells, different ribbon thicknesses, and different panel configurations. In the example shown in FIG. 6A. the ribbons are assumed to be Cu ribbons.

From FIG. 6A. one can see that for 200 μm thick ribbons, the ribbon-resistance-induced power loss for a five-inch cell with a single busbar (SBB) (at the center) configuration is 2.34%, compared to the 1.3% power loss of the double busbar (DBB) configuration. To limit the power loss to less than 2% in order to take advantage of the 1.8% power gain obtained from the reduced shading by eliminating one busbar, the thickness of the single stringing ribbon needs to be at least 250 μm. For larger cells, such as a six-inch cell, the situation can be worse. For the single center-busbar configuration, ribbons with a thickness of 400 um are needed to ensure less than 3% power loss in the six-inch cell, as indicated by cells 602 and 604. Note that the number of cells in a panel also affects the amount of power loss.

400 um is the upper boundary for the ribbon thickness because thicker ribbons can cause damage to the cells during the soldering process. specifically, thicker ribbons may result in warping of the cells, which can be caused by stress and the thermal-coefficient difference between the ribbon material and the semiconductor material. over, reliability concerns also start to surface if the stringing ribbons are too thick. Implementation of ultrasoft ribbons can reduce the stress and warping issues, but a different stringing scheme is required to effectively reduce the power loss to less than 2% without giving up the gains made by busbar shading reduction and ribbon cost reduction. In some embodiments, other methods are used to reduce stress and warping, including but not limited to: introducing crimps or springs within the length of the stringing ribbon, and spot soldering of the thick ribbon.

For the single-edge-busbar configuration, because the tabs are much wider and shorter than the stringing ribbon, the amount of power loss induced by the series resistance of the single tab is much smaller. FIG. 6B presents a diagram comparing the power loss difference between the stringing ribbons and the single tab for different ribbon/tab thicknesses. From FIG. 6B. one can see that the power loss due to the series resistance of the single tab is much smaller compared with that of the single ribbon, as indicated by column 606. For example, the power loss caused by the 250 um thick single edge tab is merely 0.73% for five-inch, 96-cell panel layout, and around 1.64% for six-inch, 60-cell panel layout. Hence, one can see that, even for the six-inch cell in the 72-cell panel, an edge tab with a thickness of 250 um is sufficiently thick that it induces less than a 2% power loss, making it possible to achieve an overall power gain considering the reduction in shading.

One more factor that can affect power output of the solar panel is the mismatch among cells, which may be caused by a partially shaded solar panel. To maximize power output, it is possible to incorporate maximum power point tracking (MPPT) devices into a solar panel to allow a partially shaded or otherwise obscured panel to deliver the maximum power to the battery charging system coupled to the panel. The MPPT device can manage power output of a string of cells or a single cell. In some embodiments of the present invention, the solar panel implements cell-level MPPT, meaning that each solar cell is coupled to an MPPT device, such as an MPPT integrated circuit (IC) chip.

Implementing MPPT at the cell level makes it possible to recoup up to 30% of the power that can be lost due to the mismatch inefficiencies. over, it eliminates cell binning requirements and may increase yield. This can thus significantly enhance the return of investment (ROI) for the array owners by eliminating the inventory management needs of installers to match panels within a string, as well as reducing warranty reserves because replacement panels no longer need to be matched to the old system. Cell-level MPPT can also increase the available surface area for the installation of a solar array, particularly in situations where there may be structural shading of the array at certain hours of the day or during certain seasons of the year. This is particularly useful to bifacial modules which may experience shading at both the front- and back-side. The cell-level MPPT also allows more flexibility in the system mounting, making it possible to use 1- or 2-axis trackers, and ground mounting on high diffuse light background. Details about the cell-level MPPT can be found in U.S. patent application Ser. No. 13/252,987 (Attorney Docket No. SSP10-1011US), entitled “Solar Panels with Integrated Cell-Level MPPT Devices,” by inventors Christopher James Beitel, Jiunn Benjamin Heng, Jianming Fu, and Zheng Xu, filed 4 Oct. 2011, the disclosure of which is incorporated by reference in its entirety herein. In further embodiments, the solar module can have one MPPT device per string of solar cells, thereby facilitating string-level MPPT.

FIG. 7A presents a diagram illustrating one exemplary placement of maximum power point tracking (MPPT) integrated circuit (IC) chips in a solar panel with double-busbar solar cells, in accordance with an embodiment of the present invention. In the example shown in FIG. 7A. the MPPT IC chips, such as an MPPT IC chip 702, are placed between adjacent solar cells. specifically, the MPPT IC chips can be placed between the two stringing ribbons. In some embodiments, the MPPT IC chips can make contact with both stringing ribbons and facilitate the serial connection between two adjacent solar cells.

FIG. 7B presents a diagram illustrating one exemplary placement of maximum power point tracking (MPPT) integrated circuit (IC) chips in a solar panel with single-center-busbar solar cells, in accordance with an embodiment of the present invention. Like the example shown in FIG. 7A. the MPPT IC chips, such as an MPPT IC chip 704, are placed between two adjacent solar cells. In some embodiments, the MPPT IC chips are three-terminal devices with two inputs from one cell and one output to the adjacent cell. The two inputs can be connected to the top and bottom electrodes (via corresponding stringing ribbons) of the first solar cell, and the one output can be connected to the top or bottom electrode of the adjacent solar cell to facilitate the serial connection between the two cells.

In addition to placing the MPPT IC chips in between adjacent solar cells, it is also possible to place the MPPT IC chips at the corner spacing between solar cells. FIG. 7C presents a diagram illustrating one exemplary placement of maximum power point tracking (MPPT) integrated circuit (IC) chips in a solar panel with single-edge-busbar solar cells, in accordance with an embodiment of the present invention. In the example shown in FIG. 7C. the MPPT IC chips, such as an MPPT IC chip 706, are placed at the corner spacing between solar cells. In some embodiments, the MPPT IC chips are in contact with the single tabs to facilitate the serial connection between the two adjacent chips. Note that for the single-edge-busbar configuration, wiring outside of the solar cell may be needed to connect the front and back electrodes located on opposite sides of the solar cell with the two inputs of the MPPT chip.

FIG. 7D presents a diagram illustrating the cross-sectional view of an exemplary solar module implementing cell-level MPPT, in accordance with an embodiment of the present invention. In FIG. 7D. each solar cell in solar module 710 includes a top electrode and a bottom electrode, which can be the single center busbars shown in FIG. 7B. Each MPPT IC chip includes a top input terminal, a bottom input terminal, and a bottom output terminal. For example, MPPT IC chip 712 includes a top input terminal 714, a bottom input terminal 716, and an output terminal 718. Top input terminal 714 and bottom input terminal 716 are coupled to top and bottom electrodes of a solar cell. Output terminal 718 is coupled to the bottom electrode of the adjacent solar cell. In the example shown in FIG. 7D. the solar cells, such as a solar cell 720, can be double-sided tunneling junction solar cells.

The solar cells and the MPPT IC chips are embedded within an adhesive polymer layer 722, which can later be cured. Materials that can be used to form adhesive polymer layer 722 include, but are not limited to: ethylene-vinyl acetate (EVA), acrylic, polycarbonate, polyolefin, and thermal plastic. Solar module 710 further includes a front- side cover 724 and a back- side cover 726. For bifacial modules, both front- side cover 724 and back- side cover 726 can be made of glass. When adhesive polymer layer 722 is cured, front- and back-side covers 724 and 726 are laminated, sealing the solar cells and the MPPT IC chips within, thus preventing damage caused by exposure to environmental factors. After lamination, solar module 710 can be trimmed and placed in a frame 728, and is then ready to be connected to an appropriate junction box.

FIG. 8 presents a flow chart illustrating the process of fabricating a solar cell module, in accordance with an embodiment of the present invention. During fabrication, solar cells comprising multi-layer semiconductor structures are obtained (operation 802). In some embodiments, the multi-layer semiconductor structure can include a double-sided tunneling junction solar cell. The solar cells can have a standard size, such as five inch by five inch or six inch by six inch. In some embodiments, the smallest dimension of the solar cells is at least five inches. Front- and back-side metal grids are then deposited to complete the bifacial solar cell fabrication (operation 804). In some embodiments, depositing the front- and back-side metal grids may include electroplating of Ag- or Sn-coated Cu grid. In further embodiments, one or more seed metal layers, such as a seed Cu or Ni layer, can be deposited onto the multi-layer structures using a physical vapor deposition (PVD) technique to improve adhesion of the electroplated Cu layer. Different types of metal grids can be formed, including, but not limited to: a metal grid with a single busbar at the center, and a metal grid with a single busbar at the cell edge. Note that for the edge-busbar configuration, the busbars at the front and back surface of the solar cells are placed at opposite edges.

Subsequently, the solar cells are strung together to form solar cell strings (operation 806). Note that, depending on the busbar configuration, the conventional stringing process may need to be modified. For the edge-busbar configuration, each solar cell needs to be rotated 90 degrees, and a single tab that is as wide as the cell edge and is between 3 and 12 mm in length can be used to connect two adjacent solar cells. In some embodiments, the length of the single tab can be between 3 and 5 mm.

A plurality of solar cell strings can then be laid out into an array and the front-side cover can be applied to the solar cell array (operation 808). For solar modules implementing cell-level MPPT, the MPPT IC chips are placed at appropriate locations, including, but not limited to: corner spacing between solar cells, and locations between adjacent solar cells (operation 810). The different rows of solar cells are then connected to each other via a modified tabbing process (operation 812), and then electrical connections between the MPPT IC chips and corresponding solar cell electrodes are formed to achieve a completely interconnected solar module (operation 814). specifically, the top electrode of a solar cell is connected to one terminal of the IC and the bottom electrode is tied to another terminal of the IC via typical semiconducting methods, including, but not limited to: solder bumps, flip chip, wrap through contacts, etc. Subsequently, the back-side cover is applied (operation 816), and the entire solar module assembly can go through the normal lamination process, which would seal the cells and MPPT ICs in place (operation 818), followed by framing and trimming (operation 820), and the attachment of a junction box (operation 822).

The foregoing descriptions of various embodiments have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention.

How do you build your own solar panel system?

Solar panels are a great option for renewable energy generation, and you can even build them on your own.

Building your own solar system to harness solar energy is a big undertaking, but for many DIY-ers or anyone interested in engineering, it can be a fun and rewarding project.

Building an entire system yourself will take a lot of research and planning, including sourcing the right materials and getting the proper permitting from your town.

It makes the most sense if you want to build a panel for a small project like as backup power for an RV. We do not recommend building your own solar panel system for use on your home, there are too many errors that can occur and lead to unsafe panels.

We will walk you through what you need to know, review the pros and cons of DIY panels, and why working with a professional installer may be a safer bet.

Is it possible to build your own solar panels?

Yes, it is possible to build your own solar system. and even the solar panels. from scratch. However, it can be risky since faulty workmanship will lead to breaks and system failure.

Solar panels are made by soldering together solar cells into strings, joining these strings together, and connecting them to a junction box. Once joined together, the components must be sealed so that the active parts of the solar panel are waterproof. Then the front is sealed with a transparent waterproof product for protection. Silicon is then used to seal the panel around the edges so that moisture does not get in.

It is not technically difficult to make a single solar panel, it is mainly soldering wires and solar cells.

The biggest issue is finding quality material to build the panels. Normally, the materials are purchased in an ad hoc fashion from many different distributors, so quality is hard to track. Building solar panels from non-quality equipment can lead to damaged panels or risk of fire from faulty craftsmanship.

If you want to build your own panels, we recommend building them on a smaller scale, for things like running electricity to your shed, instead of an entire house. Small projects will keep power demands low, which makes DIY installation manageable and less likely to break.

For someone with little to no experience in solar equipment, it can be dangerous to build and install a system large enough to power your home.

How do I build a solar panel system?

You can follow the step-by-step process below.

Note, before sourcing your equipment, it is important to keep in mind that solar cells offered on websites are usually seconds that didn’t make it past quality control. They can be chipped, blemished, or otherwise damaged, which is definitely not ideal.

How to build a solar panel system

Step 1	Design and determine size of your system
Step 2	Purchase components for solar panels
Step 3	Purchase inverters and racking
Step 4	Install racking
Step 5	Connect solar panels to racking
Step 6	Install solar inverter

Design and determine the size of your system based on your energy needs

To determine how many solar panels you will need, you need to know how much energy you plan to use on average per month, and how much sun exposure you can expect throughout the year. Once you know that, you can pick out which brand and model of solar panel will make sense for you.

If you are building panels for a small project or appliance, you will need fewer panels. Simply determine the kWh the appliance will require, then figure out how many panels to build from there.

Purchase the components that make up a solar panel

Solar cells
Pre-soldered wiring
Non-conductive material (wood, glass, or plastic)
Plexiglass

Solar cells

Solar cells are what converts the sun’s energy into electricity, each solar panel consists of about 36 solar cells.

Pre-soldered wiring

Buying pre-soldered tabbing wire will cut some steps out of the process, but you will still need a soldering iron to solder the wiring to the back of the solar cells and string the wire correctly to connect the solar cells.

Non-conductive material to attach the cells to, like wood, glass or plastic

For DIY solar panels, wood usually works best as backing because it is easy to drill holes for the wiring. Once you have your solar cells wired together, you can glue these to the wood backing and then attach all of the wires and solder each solar cell together.

After wiring, you then connect these wires to a charge controller, which regulates the volts of energy. Wood can also be used to build a box to protect the solar cells and then to lay the plexiglass on top for moisture protection.

Seal the solar panel with plexiglass

Once your solar cells are wired and glued to the wood backing, you need to seal them with plexiglass for protection from heat, debris, and moisture.

Purchase additional solar equipment like inverters and racking

If you do not trust yourself to build solar panels from scratch, you can purchase a solar panel kit which will come with more specific instructions (and usually racking) to help secure your panels. Purchasing a solar kit might actually be more useful since it will include racking already.

Racking is tricky, you will need to determine which racking equipment works for your specific roof type or ground mount. There is almost an overwhelming amount of options of clamping and mounting equipment available if you look at wholesale distributor sites.

Install the racking for your solar panels

When purchasing racking, choosing which option to buy depends on where your panels will go. For instance, will they be ground mounted, or on your RV? This will determine the type of racking you need to buy. Once you pick your racking, you need to map out where you will drill the holes to secure the racking to your structure.

Connect the solar panels to the racking equipment

To secure solar panels to the racking equipment, you will need clamps, or connectors, that are made for the racking you choose. Buying them together and from the same distributor is a good way to make sure they are built for each other. Solar panel kits generally come with racking but if you buy everything separately, make sure you do the research to build a fully functioning solar power system.

Install the proper solar inverter

Installing a solar inverter takes expertise because it will need to be hooked up the electrical grid. For this, we recommend utilizing the help from a professional installer, as they will do this safely and effectively with the right permits.

Request quotes from top-rated solar installers in your area

Are you skilled enough to build your own solar panels?

Solar panels are relatively simple enough to build, but for them to remain functional for a long period of time, they need to be built with extreme precision. Solar panels need to be able to maintain their integrity in harsh weather conditions and from consistent exposure to heat and sunlight.

Safety is the biggest concern with homemade solar panels. Moisture can get inside and ruin them and there is the potential for improperly built panels to catch fire from the sun’s heat. Mastering the soldering and electrical wiring is a challenge that generally takes the knowledge of a skilled electrician or engineer.

Building a system requires a willingness to research, make mistakes, and gain experience in electrical wiring skills and soldering techniques. So if you are an experienced engineer or electrician, this can be a bit easier to master but it is definitely not a quick weekend’s worth of DIY-ing.

How do you build your own solar panel system with a kit?

While building solar panels from scratch and then retrofitting an entire solar system is possible, most people usually want to build a solar system from pre-made equipment and then install the system.

The main advantage of buying a packaged solar kit, like one from Grape Solar versus buying all of the material separately, is that the equipment within the kit is guaranteed to work together. That is not necessarily the case if you buy each item ad hoc. For example, certain solar panels and inverters can only work with each other within defined electrical specifications.

Solar panel kits come with most of the parts you will need to complete your small-scale solar project. Image source: Amazon

Unless you’re determined to build a system from the ground up, a solar panel kit is a better option and will be less expensive and confusing.

What are the pros and cons of DIY solar panels and solar systems?

Most DIY projects have their pros and cons, but because solar systems deliver electricity to your home, having properly made panels is very important. It is the difference between saving a few thousand dollars versus having solar panels that you know will be safe.

As you can see, the cons greatly outweigh the pros.

Pros and cons of building your own solar system

Plans and instructions are available	Can cause fires
Can be a great learning experience	Materials can be poor quality or sold second-hand
Homemade systems often violate electrical codes
Not eligible for rebates or tax credits
Warranties will be invalid

Pros

Plans and instructions are readily available online at little to no cost. Being able to follow the steps to building a panel is definitely possible, but it is a large project to take on.
Manufacturing your own solar panels for small off-grid projects can be a great learning experience. If you have an engineering mindset and are curious about how solar panels work, this could be a fun challenge for you.

Cons

Homemade solar panels configured incorrectly can cause fires due to intense heat buildup on hot, sunny days.
If you choose to buy secondhand from sites like eBay, you’re likely purchasing factory seconds, rejected, or damaged solar cells. Buying any of those materials is bound to lead to system failure.
Homemade systems often violate electrical codes, this will lead to issues in permitting. It’s easier to rely on a solar company to handle electrical codes.
Homemade panels are not eligible for incentives, like the federal tax credit, or rebates which help bring down the cost of home solar systems.
Warranties on any parts will be invalidated, model warranties are usually only covered if installed by a professional.
The amount of money you save might have a short shelf life. If your panels break, you will be on the hook for that cost. Not to mention, homemade panels will not last as long as professionally-built panels.

How much does building your own solar panel system or solar panel kits cost?

Solar panel kits range in price; a 6kW system can cost anywhere from 7,000. 18,000 before the 30% federal tax credit. However, this does not include permitting costs or installation, which is included if you work with a professional.

As of March 2023, the average cost of a 6kW system is 18,000 before the tax credit; which would make the system 12,600. This relatively higher cost is worth it because it comes with a system you can trust for a lifespan of 25 years.

As for building solar panels from scratch, the costs of solar cells, wiring, inverters, permitting, etc. does vary, and it might add up to be less than the cost of working with a professional. But, these panels might not work and you will not have manufacturer support or warranties to rely on if your system stops working or you have questions.

What are other benefits of professional installations?

The cost of a solar system installation can be intimidating. however, there are many financing options like solar loans, as well as incentives for homeowners that can drastically reduce the price.

While solar system installation costs are expensive, installers have decades of hands-on experience – something no amount of research or instructions can duplicate.

The federal tax credit was extended to 30% until 2032. To reiterate, you would not be eligible for this incentive if you built and installed the panels yourself.

DIY solar panels and solar systems are possible but are best left for science projects or small-scale use. Professional installations might not give you the satisfaction of completing a project, but they can give you peace of mind.

How To Make Solar Panels

Solar panels that are commercially available cost a lot. However, you can create the solar panels you want by starting from scratch. To construct the solar panels of your choice you’ll have to construct a frame, purchase the solar panels, connect them. create an enclosure for the panels, then wire the panel and finally mount your solar panel in its entirety.

Solar power is a booming business. By using this renewable source of solar energy electricity can be produced that is not harmful to the environment or decreases the carbon footprint. It also aids in reducing the cost of electricity.

One of the benefits of creating the solar panels yourself is they’re cheaper and you can design the solar panel to your needs for power. Here are the steps you need to follow to build an at-home solar panel.

Steps to manufacture solar panels

Step 1: Making frames to hold your solar panels

It is the first thing to do. design an enclosure that will house the solar panel.

This frame is designed to protect the internal elements of the solar system from mechanical and thermal tensions. Solar cells are extremely delicate and require protection by frames. Frames also provide mount attachments.

The frame must not have sharp edges, and it must be mechanically and electrically conductory and earthed all over. It could be constructed from glass, wood, or plywood, as well as plastic.

Step 2: Purchase Solar cells

Solar cells are composed of semiconductor material i.e. silicon. These cells absorb sunlight’s energy and convert it to direct current (DC) that is later transformed into AC through an inverter. The AC is utilized to power homes.

compare, reviews, solar, online, tabbed, cells

There are many producers of solar cells, and the most reliable solar cells are produced from China, the United States, China, or Japan. Chinese sellers offer lower solar cells, however, there is no guarantee. American producers offer higher quality and expensive solar cells.

The number of cells you purchase will depend on the energy you intend to produce with the solar panels. Below are a few things to keep in mind when purchasing solar cells.

Solar cells are very fragile, so make sure you purchase extras.
The solar cells have wax for protection. The wax can be removed from the cells by submerging them in hot, but not boiling water.
Solar cells are easily available on the internet through retailers like eBay or you could make them yourself by starting from scratch.
Each cell shouldn’t be less than 1-2 per watt.
Cells for solar power were made in various dimensions with the standard solar cell measuring 6 inches in width. It can produce 1.75 watts per. If you’re looking to increase the energy, get larger solar cells.
Monocrystalline solar cells can be costly. The most efficient cost-to-efficiency alternative is to use polycrystalline solar cells.

Step 3: The solar cells should be stabbed

Tabbing solar cells is the procedure that connects the individual solar cells to form an entire photovoltaic module.

There is a possibility of purchasing solar cells that are pre-tabbed, but they’re more expensive. Tabbing a solar cell is an important process, and precautions should be taken before tabbing solar cells. A few precautionary measures are listed below:

Wear gloves when working with solar cells.
Solar cells must be handled with extreme care since they’re extremely fragile.
When soldering, put on masks or safety goggles to shield your eyes from flicking solder as well as fumes.

How to Tabbing at the solar cell

Solar cell tabbing is accomplished by soldering an electrical wire into the contact points of solar cells. The steps for the process of tabbing solar cells are as follows:

Put your solar cell on an uncluttered surface with the negative side facing upwards.
The flex pen rubs over the lines that run both up and down on the solar cells. These lines are known as contact strips.
Cut the pieces of tabbing wire taking into consideration the size of every piece must be at least twice the diameter that the solar cells are. In the case of a solar array that is 2 inches tall the cut pieces of wire must be 2 times 2 = 4 inches long.
Pick up the wire that is tabbing and put it onto the strips of contact. Tabbing wire is coated in solder already. Warm the soldering iron and connect the tabbing cable into the solar cells.

If you do not want to go through the whole process, you could purchase pre-tabbed solar cells and bypass this step.

Step 4: Test the cells of solar power

The testing of solar cells is an essential task since a malfunctioning solar cell could affect the efficiency of the entire solar panel. The solar cell must be tested for the voltage and the current.

Voltage Testing

The solar cell should be placed in the light.
Connect the black wire of the multimeter into the black port and its red wire into the port for voltage to test the voltage.
Put the solar panel on a smooth surface with the positive side facing upwards.
The black lead of the multimeter should be connected towards the panel’s negative side while the other lead is to the solar panel’s positive contact.
Check the voltage reading displayed on your multimeter. The voltage for a typical 1.75-watt solar panel should equal approximately 0.5 voltage. If the voltage is lower than 0.5 Volts, the solar cell is likely to be damaged.

Current Testing

The solar cell should be placed in the light.
Plug the black wire in the port of your multimeter. Plug the connect the red one to the port Amps port. This will determine the current value.
Turn on multi-meter. Adjust the dial on the multi-meter to the amps setting.
Set the solar cell on a clean surface, with its positive side facing upwards.
The black lead of the multimeter should be connected to the solar panel’s negative contacts while the other lead is to the solar panel’s positive contact.
Take note of the current value of the multimeter. This is the current reading of a standard 1.75-watt solar cell must be approximately 3.5 amps. If the current value is lower than 3.5 amps, the solar cell is likely to be damaged.

Step 5: Setting up the solar panel’s front and back sides

After testing the solar cells following is the process to create both the back and front sides that the panel. The front part of the panels will consist of a clear piece of acrylic. The back will be covered in white acrylic sheets. Solar cells are set between the two sheets. Sheets made of acrylic are highly preferred since they are weatherproof, durable, and resistant to corrosion.

The dimensions of the two sheets should be equal to the dimension of the panel. When calculating the dimensions, you should take into account that the cells don’t connect and that there are approximately 0.25 inches of distance between the solar cells. Also, be sure to leave about 1 to 2 inches of extra space at the edge of your solar panel to leave enough space for the frame as well as other wires. Cut the two sheets of acrylic after completing the dimension calculations.

Step 6: Assembling solar cells

In this stage, you will need to plan the physical arrangement that solar cells will be placed on the frame. Then, begin linking the solar panels with each other. Solar cells need to connect in series to obtain maximum voltage.

For instance, when there are 36 solar cells (63 watts) The layout might comprise four strings (columns composed of solar cells) each with nine solar cells that are connected in series. Let’s look into the specifics about how solar cells can be joined to each other in series.

The bottom of the solar cell’s the positive side while the top is the opposite side.
Set both solar cells onto a smooth surface, with the positive sides facing upwards
Make use of the soldering iron to join these two solar cells using the Tabbing wire.
Similar to soldering batteries, the positive side of the initial solar cell is linked to both sides of the second solar cell.

Follow the steps above for connecting the remainder of solar cells. Join the cells in such a way as until you reach an appropriate voltage, which is 12 Volts to 24 Volts. This voltage is needed to activate a 12 or 24 Volt Inverter. The inverter converts 12/24 Volts of DC into 110/220 Volts AC power.

Step 7: Check the strings of solar cells

Once you’ve connected your solar cell examine the strings to confirm they’re working correctly and delivering the correct Volts and amps. Put the strings of solar cells under the sunlight and use a multimeter to measure the current and voltage emanating from each solar cell on each string.

Step 8: Connect the strings to the acrylic backing

The solar cell’s strings are connected to acrylic sheets (backing) made in step 5. Here are the steps when attaching the strings on the backing.

Lay the sheet of white acrylic on the unclean area.
Put the stringers on the surface with the positive side facing toward the sky.
Apply some silicon on the positive side of every solar cell in every string.
Set all strings in different positions (positive to negative, and then positive, and the cycle continues) on the backing of the acrylic. This alternative method of connecting strings is known as series wiring. It can help increase the overall voltage that the panel receives.

Step 9: Connecting the strings of the solar panel

After you have secured the solar cell’s strings with backing, the following step is to connect the strings. To do this, bus wire (a large wire) is utilized. Make use of the soldering iron, flux, and solder to join the strings.

Step 10: Installation of the junction box

In this phase, we’ll install the junction box on the rear of the solar panel.

Make a hole that is the dimensions that the chase nipple will pass through in front of your panel and the junction box. The chase nipple should pass through this hole at the rear of the panel to the junction box.
Utilizing silicon, the line can attach the junction box to one end of the solar panel. Press gently on the junction box, and wait for silicon to completely dry.
Connect two terminals in the junction box with assistance from silicon.
Place the chase nipple in the junction box through the hole that was drilled earlier.
Connect the two wires of low gauge through the chase the nipple.
Connect the low-gauge black wire bus wire’s contact point, and the Red gauge wire connects to the positive bus contact point on the solar panel.
Repeat the step above to the opposite part of the panel.
The red wire should be connected to any of the connectors (4 connections total) on the terminal strip, and connect the black wire to the other connection in the terminal strip. For connecting these wires to one of the terminal strips, just unwind the screw and run your wire over it, and then tighten it.
Similar to, two additional wires will be connected to the bottom of the strip of terminals.
The other wire will be connected to the inverter, which converts DC power to AC power.

Step 11: Put together the solar panel

The last step is to assemble the entire system. Put the clear acrylic sheet that was cut before putting it on the uppermost part of your solar panel. Place the entire panel in the frame you created in step 1. It is now ready and you can test its performance afterward to confirm that it’s functioning effectively.

How To Build A Battery Bank For Solar

You can create your bank of batteries to complement the solar panels you have. Below are the steps to follow to build the battery bank of your choice.

Calculate your load

The load is the amount of power you normally use daily. It is easy to figure this out by looking through your electric bills for the past 12 months. Divide that number by 365 to determine the value of your daily usage.

Find the power capacity required

After calculating the load then you need to figure out the amount of backup power you will require. In general, most people require an emergency backup of 2 to 4 days.

Connect batteries

There are two ways to connect several batteries. Each has its distinct pros and cons.

Batteries are connected in series by connecting their positive terminals of one to the negative ends of another. This arrangement produces an increase in voltage.

Battery connections are made in parallel, by joining the positive terminal of one to its positive terminal from the following (and each terminal that is negative connects to the following positive terminal). This arrangement boosts the power of the bank through increasing amp-hours.

The size of the inverter

The inverter is a crucial component of the solar panel. It converts AC output from the solar panel and the energy stored in batteries to usable AC. The inverter doesn’t contain storage capacity, but it must be large enough for the full workload that is placed on it when it converts the energy.

The size of the inverter needs to be similar to the size of the solar system roughly. For example, a five KW(kilowatt) solar panel needs to include a 5000-watt inverter that is working optimally.

Pros and cons of building your own solar system

Instructions and plans are accessible online for download for free. The ability to follow the steps of making a panel is possible, but it’s an enormous undertaking to embark on.
Making the solar panel of your choice for smaller projects off-grid can be an excellent experience for learning. If you’ve got an engineering background and are interested in understanding the workings of solar panels it might be a great opportunity for you.
Solar panels made by homes that are not properly configured could cause fires because of extreme heat buildup during a hot days, sunny days.
If you decide to purchase secondhand items from websites such as eBay you are likely purchasing rejects, factory secondhand damaged, or defective solar cells. Any of these materials will fail the system.
DIY systems are often in violation of the electrical code and can cause issues with permits. It is easier to trust solar companies to manage electrical codes.
The panels made by homemade solar panels aren’t eligible for incentives, such as those offered by the Federal taxcredits or rebates that can reduce the cost of solar panels for home systems.
Warranty on any part will be void. Model warranties are generally only covered when installed by a professional.
The amount you save could have a limited shelf life. If your panels fail and you have to pay for them, you’ll be responsible for the expense. In addition, DIY panels won’t endure as long as professionally constructed panels.

What Materials Do You Need To Make A Solar Panel?

Solar cellsSolar Bus wireSolar tabbing wireFlux PenSoldering ironSilicon sealantGauge wireGlass or wood, or aluminumDrills and screwAcrylic sheetsMulti-meterWire Cutter

Is It Cheaper To Build Your Own Solar Panels?

DIY solar panel installation is more affordable however, your choices are restricted. According to EnergySage Solar Marketplace, the average total cost of getting solar power for homes (meaning the cost before rebates and incentives are taken into consideration) is 16,860.

Is It Possible To Build Your Own Solar Panels?

If the solar panel is installed your home will generate its own, clean, emission-free electric power. If you’re a DIY enthusiast you can construct the solar system of your choice. Building your own solar system to harness solar energy is a big undertaking. In certain cases, you could even construct yourself solar panels but the extent to which you can make with your own home solar will depend on how much you’re looking to use it for.

Are You Skilled Enough To Build Your Own Solar Panels?

It can be easy to build a solar panel but to be functioning for a lengthy duration, they must be constructed with the highest level of accuracy.

Do Solar Panels Save Money?

The solar panels, as well as the systems, can save you money and will yield a profit from your investment in a short time. The rising value of your property, the reduction in the cost of utilities along the Federal tax credit reduce the initial costs for installing your own solar panel system.

Can I Install My Own Solar Panels?

Based on a report of Energy Sage Solar Marketplace, the design and installation of the solar panel will cost around 10 percent of the total cost. If you can install solar panels, there is a good chance that a significant amount of money could be saved. A handyman who has professional experience can create and set up solar panels, but it is highly recommended to employ an expert certified to install them.The solar panel lasts for about 25-30 years, therefore it is essential to consider the initial price and advantages. If you purchase the material and put it up yourself is going to cost less but the quality may be affected. The online material is not as good when compared to professional solar panels, which are backed by 20-25 years of guarantee.

Is It Legal To Live Off The Grid?

“Off-grid living” means the disconnection from grid electricity and generating your electricity using different sources such as wind power, solar power, etc. A lot of people are looking to live a greener lifestyle and an environmentally sustainable one.

Off-grid living reduces the use of fossil fuels, reduces carbon footprint, and contributes to an environmentally sustainable and clean environment. Unfortunately, it is unlawful to completely disconnect from the utility system that is owned by the public.

Certain countries permit ” grid-tied” solar power system. In a grid-tied power system, the power generated by the solar panels is utilized to power the appliances in your home. If the power generated isn’t sufficient, you can utilize grid power with it. It will result in a lower cost of electricity.

If there is excess power generated through the solar panels it is returned to the grid, in exchange for energy credits as it is part of the net-metering program. The energy credits can be used during the rainy season and in the evenings. Certain utility companies will also compensate the customer for excess power.

Related Solar News

Is an environmental and renewable energy specialist with over 10 years of expertise within the renewable and solar industry. With over a decade of experience in various organizations within the field, He runs MySolarPerks as a passion-driven project that promotes sustainable renewable energy ideas and products.

OUR DIY SOLAR PANEL ENTHUSIASTS SHOW THEIR PROJECTS

Harold lives in Florida and enjoys the sunshine not only for the beach but also for the power it produces for his DIY panels. The following ten pictures illustrate Harold building a panel using our 1.4 watt square solar panels. Click here to see Harold’s detailed instructional PDF

Preparing the backing plate, or box as Harold calls it. It is important that the material is good and stiff, an electrical insulator, and does not expand when heating in the sun. Harold chooses acrylic material.- thick plexiglas is great, so is treated plywood.

The risers are importnat as they keep the front glass from crushing the panels. Harold uses solid strips of acrylic glued to the backing plate. Sticky foam used to insulate doors also works great and does save some time.

The cells fit nicely in the panel. They will be glued using contact cement but only with a blob about the size of a quarter for each cell. Cells are only fitted once all the back tabbing ribbon is soldered as there is no taking the cells off the backing plate once the glue sets.

The cells need to be tinned before soldering on the tabbing ribbon. The part where the tabbing ribbon is to be soldered onto the busbar should be shiny. No need to worry about overheating the cell as it melts at 1400 deg. Celcius!

The tabbing ribbon needs to be tinned too. We do sell pre-tinned tabbing ribbon, however, Harold’s kit had the non-tinned tabbing ribbon.

There are the cells again.

The wires come out of the back where the junction box is then connected. If you prefer just to have the wires exitting the panel without a junction box, that will work too.

The front of the panel is made of thin plexiglas that does not have a UV protection factor. You can use shock resistant glass although without an encapsulant, glass is prone to breakage if objects are dropped on the panel. The plexiglas is more durable, yet is more prone to scratching if mistreated, such as when scraping ice from the panel in the Northern climates. In Florida, this is not an issue!

C-Channel aluminum is excellent for fitting the frame. The riser should be matched to the size of the C-channel so that the frame fits tightly with the C-channel groove properly squeezing the front and back plates.

Bruce builds his panel.

Bruce builds his panels using 5 square solar cells. Soldering the tabbing ribbon is always a delicate procedure.

The tabbing wire has to be positioned, touching the bus bars on the solar cells.

The back of the solar cell is the positive terminal of the electrical circuit produced by the cell. The tabs have to be soldered on the back of one cell to the front of the adjacent cell to make a series circuit.

Soldering flux applied to the bus bar aids in the process of making a strong and reliable solder joint. Bruce uses a flux pen, although flux paste applied manually is also an option.

All 36 cells used in Bruce’s panel are now tabbed at the back of each cell, as they are ready to be glued to the backing board and then the front of the tabs are subsequently soldered to complete the connection.

Cells are laid out for mounting.

Tabbing ribbon is used to series-connect all the cells. It is important that the soldering joints are well connected as any resistance could result in a hot spot, reducing the panel’s power output as well as making a mess of your panel.

The project is done! The ammeter is the teltale instrument to let you know how well your soldering joints conduct current. Bruce did a great job as the panel reads the current rated for that particular cell.

Ray uses the 6 cells to make his panel. Here are all the parts before the project begins.

The project is looking good so far.

And the project is complete! All of this for a fraction of the cost of a pre-fabricated solar panel!

Larry builds his panels.

Larry builds his panels using the 5 cells. Plywood is his choice for a backing plate.

Spencer tries his hand at DIY.

You can do it! Build your own panel and send us some JPG pictures. We will post them on this page with your permission!

US20100037932A1. System for simultaneous tabbing and stringing of solar cells. Google Patents

Publication number US20100037932A1 US20100037932A1 US12/477,723 US47772309A US2010037932A1 US 20100037932 A1 US20100037932 A1 US 20100037932A1 US 47772309 A US47772309 A US 47772309A US 2010037932 A1 US2010037932 A1 US 2010037932A1 Authority US United States Prior art keywords ribbons cell photovoltaic transfer arm photovoltaic cells Prior art date 2008-06-03 Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) Abandoned Application number US12/477,723 Inventor Shmuel Erez Gerald Schock Mahendran Chidambaram Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.) VSERV TECHNOLOGIES CORP Original Assignee VSERV TECHNOLOGIES CORP Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.) 2008-06-03 Filing date 2009-06-03 Publication date 2010-02-18 Priority claimed from US5844608P external-priority 2009-06-03 Application filed by VSERV TECHNOLOGIES CORP filed Critical VSERV TECHNOLOGIES CORP 2009-06-03 Priority to US12/477,723 priority Critical patent/US20100037932A1/en 2009-11-02 Assigned to VSERV TECHNOLOGIES, CORP. reassignment VSERV TECHNOLOGIES, CORP. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CHIDAMBARAM, MAHENDRAN, EREZ, SHMUEL, SCHOCK, GERALD 2010-02-18 Publication of US20100037932A1 publication Critical patent/US20100037932A1/en Status Abandoned legal-status Critical Current

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Classifications

H — ELECTRICITY
H01 — ELECTRIC ELEMENTS
H01L — SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
H01L31/00 — Semiconductor devices sensitive to infra-red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
H01L31/18 — Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
H01L31/1876 — Particular processes or apparatus for batch treatment of the devices
H01L31/188 — Apparatus specially adapted for automatic interconnection of solar cells in a module

Y — GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y02 — TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
Y02E — REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
Y02E10/00 — Energy generation through renewable energy sources
Y02E10/50 — Photovoltaic [PV] energy

Y — GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
Y10 — TECHNICAL SUBJECTS COVERED BY FORMER USPC
Y10T — TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
Y10T29/00 — Metal working
Y10T29/49 — Method of mechanical manufacture
Y10T29/4935 — Heat exchanger or boiler making
Y10T29/49355 — Solar energy device making

Abstract

A method for stringing photovoltaic (PV) cells together and a system for the combined tabbing and stringing of photovoltaic (PV) cells for assembly into solar cell arrays. Multiple ribbons are first soldered simultaneously (or nearly so) to the front and back surfaces of individual PV cells (tabbing). After tabbing, PV cells are then loaded into a stringer subsystem which solders the front side ribbons of a first PV cell to the back side ribbons of the neighboring PV cell to form strings of PV cells wired in series. The tabber stringer system then loads completed strings into a frame containing a solar cell array being manufactured. The dual-ribbon method of PV cell interconnection reduces the electrical resistance between the cells in a string, thereby raising the solar cell array output power.

Description

This application is a NONPROVISIONAL and claims the priority benefit of U.S. Provisional Patent Application 61/058,446, filed Jun. 3, 2008, which is incorporated herein by reference.

This invention relates to the manufacture of solar cell arrays, and, in particular, to photovoltaic device interconnection methods and related apparatus for solar cell manufacturing.

Traditionally, photovoltaic (PV) cells are interconnected using a “tabbing and stringing” technique of soldering two or three conductive ribbons to the front surface of a first solar cell and to the back surface of an adjacent cell. Typically, N (where N could be ten or twelve) PV cells are interconnected in this manner across one dimension of a solar array being manufactured. The process of attaching the ribbons to the PV cells is called “tabbing” and the process of connecting multiple PV cells together is called “stringing”. A typical solar array might have “strings” of N PV cells connected together in series, where a number, M, of strings (e.g., six) are then electrically connected together in parallel. The power output of the completed solar array is then the product of the voltage generated by each string (N times the voltage generated by each PV cell) times the sum of the currents generated by all strings (M times the current of a single string). Other interconnection methodologies are also used, such as shingled interconnects with conductive adhesives to allow a continuous path for the current.

One drawback with the “tabbing and stringing” method is the poor yield and reliability of the solder joints that fail due to thermal coefficient of expansion mismatches and soldering defects. These solder joints require significant labor and capital equipment to assemble and do not allow the PV cells to be closely packed since gaps must be left between adjacent PV cells in the solar array to allow space for the tabbed electrical interconnects between adjacent PV cells.

In conventional PV cell stringing methods, a single ribbon attaches along the front surface of a first PV cell (soldered to a bus bar on the first PV cell front surface), extends past the PV cell edge, then bends down and attaches along the bottom of the neighboring cell (soldered to a bus bar on the second PV cell back surface). One aspect of the present invention includes a mono/multi crystalline silicon photovoltaic module comprising, a first photovoltaic cell (PV cell) with a top interconnect tab (ribbon) and a second photovoltaic cell with a bottom interconnect tab (ribbon). The advantage of this improved PV cell interconnection method is improved quality of the soldering of the ribbons to the PV cell bus bars since this soldering operation is done separately from the stringing operation which interconnects neighboring PV cells. Neighboring cells are instead interconnected by the separate soldering step which attaches a first ribbon from a first PV cell to a second ribbon from the neighboring second PV cell—this soldering operation may be accomplished with a soldering head separate from those used to attach the front and back surface ribbons to the bus bars on the PV cells.

Another aspect of the present invention is a system for the tabbing of PV cells—this is the process step in which ribbons are attached to the front and back surfaces (onto bus bars) of a single wafer. The front side ribbons (typically two or three) are arranged to overhang one edge of the wafer from the front surface of the wafer, and the back side ribbons (the same number as for the front side ribbons) are arranged to overhang the opposite edge of the wafer. Soldering heads are pressed against the front and back surfaces simultaneously (or nearly so) to rapidly head the ribbon to enable low-stress solder bonds between the ribbons and the bus bars on the wafer. Further ribbon-to-wafer stress reduction may be accomplished by means of a sequencing method in which only selected portions of the ribbon are heated at any one time, and the spatial relationships of the heated portions are selected to reduce the relative thermal expansion between the ribbons and the wafer, thereby enhancing ribbon-to-wafer adhesion.

A still further aspect of the present invention is a method for stringing PV cells together to form “strings” of PV cells wired in series, typically with 10 to 12 cells each. When a string is completed, it is transferred to a secondary belt which supports the string prior to the loading of the string into the solar array being assembled. This method improves overall system throughput since the next string can be started before the just-completed string has been transferred into the solar array.

Another aspect of the present invention is the use of a rotary turntable including multiple bins for PV cells: For example, a system with three such bins may include a first bin from which PV cells (wafers) are loaded into the tabbing subsystem, a second bin in which PV cells are loaded by the system operator or an external robotic apparatus, and a third bin for storage of rejected PV cells. When all the PV cells have been loaded into the tabbing system from the first bin, the turntable rotates to position the second bin for loading PV cells into the tabbing subsystem while new PV cells are being loaded into the first bin. This aspect of the present invention improves throughput since the tabber stringer system experiences minimal idle time waiting for PV cells to be loaded.

FIG. 1 shows a close-up isometric view of the tabber-stringer system performing the wafer pickup operation.

FIG. 2 shows an isometric view of a complete tabber-stringer system configured in accordance with an embodiment of the present invention.

FIG. 3 shows a close-up isometric view of a tabber-stringer system configured in accordance with an embodiment of the present invention.

FIG. 5 shows a close-up isometric view of a complete tabber-stringer system performing the wafer align operation,

FIG. 6 shows a close-up isometric view of the tabber-stringer system performing the wafer inspection operation.

FIG. 7 shows a close-up isometric view of the tabber-stringer system performing the wafer rejection operation.

FIG. 8 shows a close-up isometric view of the tabber-stringer system performing the ribbon grabber reach-in operation.

FIG. 9 shows a close-up isometric view of the tabber-stringer system performing the ribbon grabbing operation.

FIG. 10 shows a close-up isometric view of the tabber-stringer system performing the ribbon pulling operation.

FIG. 11 shows a close-up isometric view of the tabber-stringer system after completion of the ribbon pulling operation.

FIG. 12 shows a close-up isometric view of the tabber-stringer system performing the soldering head clamping operation.

FIG. 13 shows a close-up isometric view of the tabber-stringer system performing the ribbon soldering operation.

FIG. 14 shows a close-up isometric view of the tabber-stringer system after completion of the ribbon soldering operation.

FIG. 16 shows a schematic top view of a PV cell, illustrating the zones for soldering the ribbon to the wafer.

FIG. 17 shows a close-up isometric view of the tabber-stringer system performing the wafer transfer to the belt operation.

FIG. 18 shows a close-up isometric view of the tabber-stringer system performing the wafer stringing operation.

FIG. 22 shows a close-up isometric view of the tabber-stringer system performing the wafer indexing operation.

FIG. 24 shows a close-up isometric view of the tabber-stringer system performing the stringing and buffering operation.

Described herein is a system configured for the combined tabbing and stringing of photovoltaic solar cells (PV cells or wafers) together, and the subsequent assembly of strings of PV cells into a solar cell array. The system includes the following main subsystems:

1) Wafer bin turntable—this turntable contains multiple (e.g., three) bins: for example, one bin containing wafers being individually loaded into the tabbing subsystem, a second bin being loaded with wafers, and a third bin for rejected wafers. In other embodiments, more than three bins may be used. For example, alternating pairs of wafer containing bins may be used to provide multiple operational positions, as will be apparent from the discussion below. This may be especially useful where tabbing and stringing operations are performed by pairs of assemblies (e.g., two such assemblies, four such assemblies, etc.).
2) Vacuum arm wafer transfer subsystem—transfers wafers between the bins, tabbing subsystem and stringing subsystem.
3) Tabbing subsystem—solders ribbons to the front and back sides of a wafer, with appropriate overhangs to enable stringing.
4) Stringing subsystem—solders wafers together to form strings of wafers up to N (e.g., 12) wafers in length.
5) Solar cell array assembly subsystem—takes completed strings from the stringing subsystem and loads them into a solar array being manufactured. A typical solar cell array may have up to at least six strings, each with twelve cells, for a total of 72 PV cells generating roughly 225 W. Each of the above subsystems in described in detail below.

FIG. 1 shows a close-up isometric view of the tabber-stringer system performing the wafer pickup operation. The turntable 106 has three base plates: base plate #1 113 which, in this example, is supporting wafer stack 111, base plate #2 116 which supports wafer stack 114, and base plate #3 118 which collects rejected wafers (see FIGS. 6 and 7 ). Guide posts 112, 115, and 117 are fixedly attached to turntable 106 and slide through holes in base plates 113, 116, and 118. An actuator (not shown) is mounted adjacent to the vacuum arm mechanism comprising arm 402 and pivot 403. For the orientation of turntable 106 shown in FIG. 1. the actuator serves to move base plate 113 up and down, thereby positioning the top wafer ( wafer 401 in this example) at the proper height to be picked up by vacuum arm 402. When turntable 106 is rotated 120° clockwise, base plate 118 is positioned over the actuator to enable rejected wafers to be removed from vacuum arm 402. When turntable 106 is rotated 120° counterclockwise, base plate 116 is positioned over the actuator to enable wafers from stack 114 to be picked up by vacuum arm 402 (see FIGS. 4A and 4B ).

Vacuum arm 402 is shown in the wafer pick-up position, on top of wafer 401. Vacuum arm 402 is a fork-like structure comprising three tines, in this example, each with a plurality of small holes and connected to a vacuum pump to exert an even and gentle clamping force to the wafer being picked up. This gentle clamping force enables thin wafers to be processed by the tabber stringer system of the present invention. Vacuum arm 402 swings around pivot 403, driven by a rotary drive actuator (not shown). Camera 100 and lens 101 are part of the wafer imaging system (see FIG. 6 ). Two or more solder reels 120 feed at least two ribbons to the front surfaces of the wafer being tabbed (see FIGS. 8-15J ). Similarly, two or more solder reels 121 feed at least two ribbons to the back surfaces of the wafer being tabbed (see FIGS. 8-15K ).

Front-side soldering heads 102, back-side soldering heads 104, front- side ribbon puller 103, back- side ribbon puller 143, and support block 105 comprise the ribbon soldering head. Belts 109 and rollers 110 serve to support and index wafers after tabbing, and during stringing. Stringer soldering heads 306 perform the stringing soldering operation. A wafer 801 with soldered-on ribbons 895 is supported by belts 109 and has been indexed over one position to await the next stringing operation. Table 107 supports solar array frame 199 during assembly of multiple strings into a solar array. Wafer 108 is shown within solar array frame 199.

FIG. 2 shows an isometric view of a complete tabber-stringer system configured in accordance with an embodiment of the present invention. Belt 302, moved by rollers 301, supports each string as it is being soldered together. Once the final wafer for each string has been soldered to the string-in-progress, the completed string is moved out onto belt 302, thereby freeing up belts 109 to support the initial wafers for the next string-in-progress. This dual belt scheme maximizes system throughput by freeing up the tabber-stringer mechanism from having to wait for completion of the array assembly operation.

Once a completed string (not shown) has been moved out onto belt 302, vacuum chuck 201 is moved down onto the completed string, which is then lifted by the vacuum force of the vacuum chuck 201, moved up by mechanism 202. Table 107, supported by table support legs 303, is movable along an axis perpendicular to the motion axis of belt 302, enabling completed strings to be loaded into solar array frame 199. Typical wafers in the first string to be loaded into frame 199 are wafers 108 and 203.

FIG. 3 shows a close-up isometric view of the tabber-stringer system embodying the present invention. In this view, vacuum arm 402 has rotated 90° from the position shown in FIG. 1 to position wafer 802 in a vertical orientation. In this position, visual inspection of wafer 802 (e.g., for defects such as cracks, chips, etc.) is accommodated (see FIG. 6 ). The wafer does not yet have the front and back ribbons soldered into place.

FIG. 4A shows a top view of the turntable in position #1. In this turntable orientation, wafer stack 111 is supported by base plate #1 113 (see FIG. 1 ), wafer stack 114 is supported by base plate #2 116, and wafer stack 119 (rejected wafers) is supported by base plate #3 118. Arrow 303 shows the direction in which wafers are individually removed by vacuum arm 402 for tabbing and subsequent stringing in the system according to the present invention. Wafer stack 114 is being loaded into the system simultaneously with the unloading of stack 111 by vacuum arm 402. This enables maximum system throughput since the system does not need to wait for wafer loading before beginning tabbing and stringing operations.

FIG. 4B shows a top view of the turntable in position #2. In this turntable orientation ( turntable 106 rotated 120° counterclockwise relative to the turntable orientation shown in FIG. 4A ), wafer stack 711 is supported by base plate #2 116 (see FIG. 1 ), wafer stack 719 is supported by base plate #1 113, and wafer stack 714 (rejected wafers) is supported by base plate #3 118. Arrow 703 shows the direction in which wafers are individually removed by vacuum arm 402 for tabbing and subsequent stringing in the system according to the present invention. Wafer stack 719 is being loaded into the system simultaneously with the unloading of stack 711 by vacuum arm 402.

The system remains in the configuration shown in FIG. 4A until all of stack 111 has been loaded into the system, then turntable 106 rotates 120° counterclockwise to position stack 711 for loading into the system as shown in FIG. 4B. Once stack 711 has been fully loaded into the system (one wafer at a time), turntable 106 rotates 120° clockwise to return to the position shown in FIG. 4A. Thus, at all times a stack of wafers is available for loading into the tabber stringer mechanism while another stack of wafers is being loaded into the system.

FIG. 5 shows a close-up isometric view of a complete tabber-stringer system performing the wafer align operation. Vacuum arm 402 has rotated away from the (vertical) inspection position, towards belts 109. The vacuum force is then relaxed, enabling wafer 401 to move down against a set of alignment pins (not shown). The vacuum arm 402 is then reactivated to reclamp wafer 401. This sequence ensures that each wafer on the vacuum arm is in the same position prior to initiating the tabbing operation—this, in turn, ensures that the ribbons are always attached to the wafers in the same locations, important for ribbon-to-ribbon alignment during stringing.

An alternative method for wafer alignment is to use the imaging camera 100 to determine the position of the wafer 401 on the vacuum arm 402, and then reorient vacuum arm 402 in two dimensions to compensate for any wafer position errors prior to tabbing and stringing. This method has the advantage of higher speed (since no separate alignment step as shown in FIG. 5 is required) and also possibly lower wafer damage since no sliding of the wafer relative to the vacuum arm 402 is required. The disadvantage of this alternative alignment method is the requirement for two-dimensional movement of the vacuum arm relative to the ribbon soldering mechanism and belts 109.

FIG. 6 shows a close-up isometric view of the tabber-stringer system performing the wafer inspection operation. Wafer 401 is backlit by an illuminator (not shown). Camera 100 then images wafer 401 through lens 101, forming an image which is acquired by a computer-based image analysis system (not shown). The image analysis system processes the wafer image, looking for cracks or chips in the wafer (typically around the wafer edges). If the alternative wafer alignment method described above is used, the image analysis system also locates the edges of the wafer in two dimensions and determines a wafer positional error vector. This positional error vector is then used by the vacuum arm actuation mechanism to displace the vacuum arm (and thus the wafer clamped to it) by the proper amount to enable the front and back ribbons to be soldered in the proper positions.

After the image analysis system has processed the wafer image and determined whether the wafer is damaged, a decision is made: should the wafer be used in the solar array being manufactured or should the wafer be rejected? The criterion for rejection is a pre-determined degree of acceptable damage to the wafer. If the degree of damage is below the acceptable limit, then the wafer can be used in the solar array being manufactured and vacuum arm 402 will remain in the vertical position to enable soldering of the front and back ribbons to the wafer in the “tabbing” operation. If the degree of damage exceeds the degree of acceptable damage, the wafer will be rejected and not stringed together with other (previously accepted) wafers.

FIG. 7 shows a close-up isometric view of the tabber-stringer system performing the wafer rejection operation, following a decision (with respect to the inspection process described in conjunction with FIG. 6 ) that the degree of damage to the wafer exceeds acceptable levels. First, turntable 106 rotates so as to position base plate #3 118 over the actuator (not shown). The actuator then moves base plate #3 118 vertically (guided by pins 117) to the proper height to accept rejected wafer 401. Now, vacuum arm 402 rotates so as to place rejected wafer 401 onto base plate #3 118 (which may already be supporting a number of previously-rejected wafers). Vacuum arm 402 then releases rejected wafer 401 and returns to a vertical position, while the actuator lowers base plate #3 118 to the bottom position. Turntable 106 then rotates to position base plate #1 113 over the actuator once again.

The actuator is designed to move vertically through three holes in turntable 106, enabling base plates 113, 116, and 118 to be moved up and down (only one at a time). During rotation of turntable 106, the actuator is lowered beneath the bottom surface of turntable 106 to enable free rotation of turntable 106.

FIG. 8 shows a close-up isometric view of the tabber-stringer system performing the ribbon grabber reach-in operation. The two front side ribbon pullers 103 are moving down as shown by arrow 730. Simultaneously, the two back side ribbon pullers 143 are moving down as shown by arrow 731. See also FIG. 15B. where arrow 980 corresponds to arrow 730, and arrow 981 corresponds to arrow 731.

FIG. 9 shows a close-up isometric view of the tabber-stringer system performing the ribbon grabbing operation. The two front side ribbon pullers 103 have moved down far enough so that front side ribbon grabber 740 can grip front side ribbon 880. The two back side ribbon pullers 143 have moved down far enough so that back side ribbon grabber 741 can grip back side ribbon 881. See also FIG. 15C.

FIG. 10 shows a close-up isometric view of the tabber-stringer system performing the ribbon pulling operation. The two front side ribbon pullers 103 are moving up as shown by arrow 732. Simultaneously, the two back side ribbon pullers 143 are moving up as shown by arrow 733. See also FIG. 15D. where arrow 982 corresponds to arrow 732, and arrow 983 corresponds to arrow 733. As front side ribbon pullers 103 move up, front side ribbon grabbers 740 pull front side ribbons 880 through front side ribbon cutters 780 and front side ribbon extenders 782 (see FIG. 15D ). As back side ribbon pullers 143 move up, back side ribbon grabbers 741 pull back side ribbons 881 through back side ribbon cutters 781 and back side ribbon extenders 783 (see FIG. 15D ). While front side ribbons 880 and back side ribbons 881 are moving up, flux applicators 122 (one per pair of front side ribbon and back side ribbon) deposit flux on the sides of the ribbons 880 and 881 facing wafer 802. See also FIG. 15E.

FIG. 11 shows a close-up isometric view of the tabber-stringer system after completion of the ribbon pulling operation. This is illustrated also in FIG. 15F.

FIG. 12 shows a close-up isometric view of the tabber-stringer system performing the soldering head clamping operation. Front side soldering heads 102 are swinging down (arrow 750) towards the front side of wafer 802. Back side soldering heads 104 are swinging down (arrow 751) towards the back side of wafer 802.

FIG. 13 shows a close-up isometric view of the tabber-stringer system performing the ribbon soldering operation—see also FIG. 15H. Front side soldering head 102 is pressed against front side ribbon 880 to ensure that it is properly soldered to the front side of wafer 802. Back side soldering head 104 is pressed against back side ribbon 881 to ensure that it is properly soldered to the back side of wafer 802. The discussion of FIG. 16. below, gives further details on the ribbon soldering process.

FIG. 14 shows a close-up isometric view of the tabber-stringer system after completion of the ribbon soldering operation—see also FIG. 15I.

FIGS. 15A-15K are schematic views of the steps illustrated in FIGS. 9-14. Wafer 790 corresponds to wafer 802 in FIGS. 8-14.

In FIG. 15A. ribbon pullers 103 and 143 are still above the upper edge of wafer 790, and the upper ends of ribbons 880 and 881 are below the lower edge of wafer 790. This view corresponds to FIG. 3.

In FIG. 15B. front side ribbon pullers 103 are moving down, carrying front side ribbon grabbers 740 towards the upper ends of front side ribbons 880. Back side ribbon pullers 143 are moving down, carrying back side ribbon grabbers 741 towards the upper ends of back side ribbons 881. This view corresponds to FIG. 8.

In FIG. 15C. front side ribbon pullers 103 have moved all the way down, placing front side ribbon grabbers 740 at the proper positions to grab front side ribbons 880. Back side ribbon pullers 143 have moved all the way down, placing back side ribbon grabbers 741 at the proper positions to grab back side ribbons 881. This view corresponds to FIG. 9.

In FIG. 15D. front side ribbon grabbers 740 are holding front side ribbons 880 while front side ribbon pullers 103 are moving upwards (arrow 982). Back side ribbon grabbers 741 are holding back side ribbons 881 while back side ribbon pullers 143 are moving upwards (arrow 983). As front side ribbons 880 move upwards, they slide through front side ribbon cutters 780 and front side ribbon extenders 782. As back side ribbons 881 move upwards, they slide through back side ribbon cutters 781 and back side ribbon extenders 783. While front side ribbons 880 and back side ribbons 881 are moving up, flux applicators 122 (one per pair of front side ribbon and back side ribbon) deposit flux on the sides of the ribbons 880 and 881 facing wafer 802. This view corresponds to FIG. 10.

In FIG. 15E. front side ribbon cutters 780 have just cut front side ribbons 880, and back side ribbon cutters 781 have just cut back side ribbons 881. This cutting operation may occur while ribbons 880 and 881 are moving upwards, or may occur after ribbon pullers 103 and 143 have momentarily stopped upwards motion of ribbons 880 and 881.

In FIG. 15F. front side ribbon pullers 103 continue to pull (arrow 984) front side ribbons 880 upwards after front side ribbons 880 were cut by front side ribbon cutters 780 (see FIG. 15E ). Back side ribbon pullers 143 continue to pull (arrow 985) back side ribbons 881 upwards after back side ribbons 881 were cut by back side ribbon cutters 781. Eventually front side ribbons 880 are pulled completely through front side ribbon cutters 780, while back side ribbons 881 are pulled completely through back side ribbon cutters 781.

In FIG. 15G. the motion of the front and back side ribbon pullers 103 and 143, respectively, diverges. Front side ribbon puller 103 continues to move upwards (arrow 986) while back side ribbon puller 143 is stopped. The reason for this differing motion is that for proper stringing (see FIGS. 18-21 ), it is necessary for the front side ribbons to be offset upwards relative to the back side ribbons. This enables the front side ribbon to hang over the upper edge of wafer 790, while the back side ribbon hangs over the lower edge of wafer 790. It is necessary for front side ribbon puller 103 to move up (arrow 986) a sufficient distance to enable front side ribbons 880 to overhang the upper edge of wafer 790 by the proper amount (typically 3-4 mm) for stringing. Similarly, it is necessary for back side ribbon puller 143 to move up a shorter distance to enable back side ribbons 881 to overhang the lower edge of wafer 790 by the proper amount (typically 3-4 mm). When this pulling operation is complete, the front side ribbons 880 and back side ribbons 881 are in the proper position for soldering in FIG. 15H (see also FIG. 13 ). Of course, in an alternative arrangement one could allow the front side ribbon to protrude over the lower edge of wafer 790 and the back side ribbon to protrude over the upper edge thereof.

In FIG. 15H. the ribbon soldering operation is illustrated. Front side soldering heads 102 have swung down (see FIG. 12 ) and are now pressing front side ribbons 880 against front side contact areas on wafer 790 ( wafer 802 in FIG. 13 ). Back side soldering heads 104 have swung down (see FIG. 12 ) and are now pressing back side ribbons 881 against back side contact areas on wafer 790. It is preferable that the front side and back side soldering heads, 102 and 104, respectively, contact wafer 790 approximately simultaneously to ensure that no unnecessary asymmetrical (front-to-back) forces are applied to wafer 790. In particular, if back side soldering heads 104 were to contact the back side of wafer 790 before front side soldering heads 102 contacted the front side of wafer 790, it is possible that wafer 790 could be disconnected from vacuum arm 402, causing either wafer misalignment or wafer damage. After soldering is complete, ribbon grabbers 740 and 741 release ribbons 880 and 881, respectively.

In FIG. 15I. the front and back side soldering heads 102 and 104, respectively, have swung back to their upper positions (see FIG. 14 ). At the same time, ribbon pullers 103 and 104 move up ( arrows 988 and 989, respectively) to position ribbon grabbers 740 and 741 above the upper edge of wafer 790. The offset configuration of the front 880 and back 881 ribbons can be seen clearly here.

FIG. 15J. wafer 790 has been moved out of the soldering mechanism towards belts 109 (see FIG. 17 ). Ribbon pullers 103 and 143 remain in their full up position. Front side ribbon extenders 782 feed front side ribbons 880 upwards through front side ribbon cutters 780 to provide a small length of ribbon for grabbing by front side ribbon grabbers 740 when tabbing the next wafer. Back side ribbon extenders 783 feed back side ribbons 881 upwards through back side ribbon cutters 781 to provide a small length of ribbon for grabbing by back side ribbon grabbers 741 when tabbing the next wafer.

FIG. 15K is a schematic view of an alternative method to that shown in FIG. 15H for soldering ribbons 880 and 881 to wafer 790. All components of the tabbing mechanism are the same as in FIG. 15H. except for the front and back soldering heads 2102 and 2104, respectively, which differ from the soldering heads 102 and 104 illustrated in FIG. 15H by the addition of a capability for blowing gas (either air or an inert gas, such as Argon or Nitrogen, for example), against the front and back side ribbons 880 and 881, respectively, during the ribbon soldering operation. Front side soldering heads 2102 blow gas 2103 against front side ribbons 880, forcing them against front side contact areas on wafer 790. Gas 2103 may be heated to aid in bringing ribbons 880 to the required soldering temperature. Front side soldering heads 2102 simultaneously heat front side ribbons 880 inductively to the required soldering temperature.

Similarly, back side soldering heads 2104 blow gas 2105 against back side ribbons 881, forcing them against back side contact areas on wafer 790. Gas 2105 may be heated to aid in bringing ribbons 881 to the required soldering temperature. Back side soldering heads 2104 simultaneously heat back side ribbons 881 inductively to the required soldering temperature.

It is preferable that the front side and back side soldering heads, 2102 and 2104, respectively, blow gas towards wafer 790 approximately simultaneously to ensure that no unnecessary asymmetrical (front-to-back) forces are applied to wafer. 790. In particular, if the back side soldering heads 2104 were to blow gas 2105 towards the back side of wafer 790 before the front side soldering heads 2102 have started blowing gas 2103 towards the front side of wafer 790, it is possible that wafer 790 could be disconnected from vacuum arm 402, causing either wafer misalignment or wafer damage. After soldering is complete, ribbon grabbers 740 and 741 release ribbons 880 and 881, respectively.

FIG. 16 shows a schematic top view of a PV cell, illustrating zones for soldering the ribbon to the wafer. Each ribbon can be heated in a number of separate sections, (where seven are shown here). The left ribbon is divided up into seven sections 241-247, and the right ribbon is divided up into seven sections 251-257. These sections do not correspond to physical structures on the ribbon, but rather, to small heater elements in either the front or back soldering heads, 102 and 104, respectively. For example, if induction heating of the front and back ribbons 880 and 881, respectively, is employed, then sections 241-247 and 251-257 would correspond to individually-controlled RF coils within the (nonconducting) solder head structures. In this case, sequence #1 in Table I would correspond to exciting all RF coils simultaneously. In general, due to differential thermal expansion between the ribbons and the wafer, such a sequence would be undesirable and might lead to wafer distortion and/or failure of the solder joint between the ribbons and the wafer. Sequence #2 would correspond to the opposite case—sequential excitation of the RF induction coils from one end of the ribbons (both front and back) to the other end of the ribbons. Sequences #3-5 correspond to intermediate approaches where several RF coils are excited at the same time.

If infrared heating is employed, the sequences can be the same as for RF induction heating, but now individual heat lamps within the front and back soldering heads are energized according to the sequences in Table I. Other heating methods for soldering are familiar to those skilled in the art—the only requirement for any of these is that there must a segmentation of the heating means corresponding to the segments shown in FIG. 16 and Table I. For maximum system throughput, it is preferable that the heater elements (of whatever type) must be able to rapidly heat up and cool down. This capability also ensures that there will be minimal overall heating of the wafer, which could cause thermally-induced stress damage.

FIG. 17 shows a close-up isometric view of the tabber-stringer system performing the wafer transfer to the belt operation. Following successful completion of the soldering operation in FIG. 13 and the subsequent swinging back of the front and back soldering heads 102 and 104, respectively, vacuum arm 402 and the vacuum-attached wafer 802 swing approximately 90° to the right to place wafer 802 onto belts 109 supported by rollers 110. Wafer 801 has already been indexed one step to the right, where the distance corresponding to a single step is the wafer dimension (parallel to belts 109) plus an additional few millimeters in addition to allow room for stringing the wafers together (see FIGS. 19-21 ). Stringer soldering heads 306 are positioned to allow wafer 802 to swing onto belts 109 unimpeded.

FIG. 18 shows a close-up isometric view of the tabber-stringer system performing the wafer stringing operation. Wafer 802 is now supported by belts 109, with vacuum arm 402 below and between belts 109. The three-tined fork design of vacuum arm 402 enables the interleaving of vacuum arm 402 with belts 109. Stringer soldering heads 306 are used to solder front side ribbons to back side ribbons as shown in FIGS. 19-21 for three different stringing methods.

FIG. 19 is a schematic side cross-sectional view of the tab-over method of stringing. Three wafers 1001-1003 being stringed are shown (1001 and 1003 are shown only partially). Insulating strips 1020 and 1021 are attached to the edges of wafer 1001 and 1002, respectively, in line with ribbons 1010-1015 ( strips 1020 and 1021 are attached prior to soldering of ribbons). Insulating strips 1022 and 1023 on the front sides of wafers 1002 and 1003, respectively, are also in line with ribbons 1010-1015 ( strips 1022 and 1023 are attached prior to soldering of ribbons). Ribbons 1010 and 1013 are soldered to wafer 1001 during the tabbing operation in FIG. 13. Similarly, ribbons 1011 and 1014 are soldered to wafer 1002, and ribbons 1012 and 1015 are soldered to wafer 1003 also during the tabbing operation. The stringing operation in FIG. 18 for this method of stringing corresponds to bringing stringer soldering heads 1030 (corresponding to stringer soldering heads 306 in FIG. 18 ) down on front side ribbons 1010 (soldered to the front side of wafer 1001), which are on top of front side ribbons 1014 (soldered to the back side of wafer 1002). Stringer soldering heads 1030 heat both ribbons 1010 and 1014 to solder them together, while insulating strip 1022 protects wafer 1002 from excessive heating. In FIG. 19. wafers 1002 and 1003 were stringed together in an earlier operation identical to that shown here.

FIG. 20 is a schematic side cross-sectional view of the extended tab method of stringing. Three wafers 1101-1103 being stringed are shown (1101 and 1103 are shown only partially). Three front side ribbons 1110-1112 and three back side ribbons 1113-1115 are shown. Front side ribbon 1110 and back side ribbon 1114 are being soldered together by stringer soldering heads 1120 and 1121 (corresponding to stringer soldering heads 306 in FIG. 18 ). Front side ribbon 1111 and back side ribbon 1115 were soldered together in an earlier operation identical to that shown here. Note that FIG. 20 illustrates the reason for the offset of the front side ribbons relative to the back side ribbons (see FIG. 15G ).

FIG. 21 is a schematic side cross-sectional view of the conductive path method of stringing. Three wafers 1201-1203 being stringed are shown (1201 and 1203 are shown only partially). In this method, the PV cells are fabricated with conductive paths (vias) 1221 and 1231 through from the front side to the back side of wafers 1202 and 1203, respectively (the conductive path is not shown for wafer 1201). This method eliminates the need for the front side ribbon to bend down between wafers (e.g., wafers 1101 and 1102 in FIG. 20 ). Since the front side ribbons remain in the plane of the wafer front sides, closer packing of PV cells within the solar array being manufactured is possible. Stringer soldering heads 1230 (corresponding to stringer soldering heads 306 in FIG. 18 ) are shown soldering front side ribbon 1210 on wafer 1201 to conductive path 1221 on wafer 1202. Conductive path 1221 was previously soldered to back side ribbon 1214 during the tabbing operation. Front side ribbon 1211 on wafer 1202 and conductive path 1231 on wafer 1203 were have already been soldered together in an earlier operation identical to that shown here.

An alternative method for electrically connecting (stringing) successive wafers together is spot welding, instead of soldering. In this case, the solder stringing heads 306 in FIG. 18 would be configured as spot welding heads. As is familiar to those skilled in the art, spot welding involves a momentary passage of a high electrical current from one welding head to an opposing welding head, through two pieces of metal which are to be spot welded together. In FIG. 19. upper spot welding head 306 could supply a momentary high current, which would then flow out of the head 306, through the two ribbons to be electrically connected together, and then into an opposing lower spot welding head. The benefit of spot welding over soldering is the substantially reduced amount of overall heating of the wafers being stringed, since the heat pulse required to spot weld the ribbons together will not spread to the wafers onto which the ribbons were soldered during the tabbing operation. Reference to FIG. 19 shows that the soldering heads 1030 would now be configured as spot welding heads. The other electrode required for the spot welding operation in FIG. 19 would have to make electrical contact to ribbon 1014 to complete the welding circuit. Reference to FIG. 20 shows that soldering heads 1120 and 1121 would be configured as upper and lower spot welding heads in this alternative embodiment. Finally, reference to FIG. 21 shows that soldering heads 1230 would be configured as spot welding heads. The other electrode required for the spot welding operation in FIG. 21 would have to make electrical contact to ribbon 1214 to complete the welding circuit.

FIG. 22 shows a close-up isometric view of the tabber-stringer system performing the wafer indexing operation. As shown in FIG. 18. vacuum arm 402 has swung to the right 90° to position wafer 802 on belts 109 supported by rollers 110. The vacuum clamping between wafer 802 and vacuum arm 402 is then turned off, freeing wafer 802 from being clamped to vacuum arm 402. Now wafer 802 is entirely supported by belts 109. Arrow 899 illustrates the motion of belts 109 carrying wafers 801 and 802 (which are stringed together) a distance corresponding to the dimension of wafer 802 parallel to belts 109 plus a small additional increment (typically a few mm) to allow room for soldering front and back side ribbons together between the neighboring wafers. As the string being assembled grows longer, the front end (wafers first stringed together) will extend out onto belt 302 supported by rollers 301 (see FIG. 2 ).

FIG. 23 shows a close-up isometric view of the tabber-stringer system resetting the vacuum arm. Once the indexing operation in FIG. 22 has been completed, vacuum arm 402 is free to swing back to the left of the figure (arrow 876). The interleaving of the tines of the fork- like vacuum arm 402 between belts 109 can be seen.

FIG. 24 shows a close-up isometric view of the tabber-stringer system performing the stringing and buffering operation. Wafers 811 and 812 are the last two wafers of the previously-completed string which is now entirely supported by belt 302 running on rollers 301. Vacuum chuck 201 is moving down (arrow 875) to lift the completed string off belt 302 for loading into the solar array frame 199 supported by table 107 on support legs 303. Wafers 901 and 902 have already been stringed together as the beginning of the next string. Note that the dual-belt configuration ( belts 109 and belt 302) enables improved overall system throughput since the loading of completed strings can take place simultaneously with the initial soldering of the next string.

The invention above has been described for the case of two interconnections ribbons per PV cell, but can be extended to the case of PV cells with any number of interconnection ribbons per PV cell, as would be familiar to one skilled in the art.

Front side and back side soldering heads have been shown as separate elements for each of the front side and back side ribbons, respectively. The front side soldering heads could be combined into one or more elements, each soldering more than one ribbon to the front side of the wafer being tabbed. Similarly, the back side soldering heads could be combined into one or more elements, each soldering more than one ribbon to the back side of the ribbon being tabbed.

Although a vacuum arm has been shown for transferring wafers between the bins, tabbing subsystem and stringing subsystem, other means of wafer transport such as electrostatic clamping arms may be used within the scope of the present invention. The vacuum arm has been illustrated as a simple swinging arm, however, more complex types of robotic wafer transport mechanisms could perform the required functions of wafer transfer between the bins, tabbing subsystem and stringing subsystem, as is familiar to those skilled in the art.

Wafers are shown being supported on multiple belts in the stringing subsystem, however other support and transfer means may be employed within the scope of the present invention, such as a single moving belt, a multiplicity of support rollers, etc.

Within the solar cell array subsystem, completed strings are shown being supported by a secondary belt mechanism, however other support and transfer means may be employed within the scope of the present invention, such as a multiple moving belts, a multiplicity of support rollers, etc.

Within the solar cell array subsystem, a single vacuum chuck is shown for lifting and placing completed strings into the solar array being manufactured. Alternative lifting and placing mechanisms are possible within the scope of the present invention, such as electrostatic clamping chucks, etc.

Claims ( 25 )

A system, comprising means for affixing a multiplicity of top interconnect tabs (ribbons) and a multiplicity of bottom interconnect tabs to a first photovoltaic cell, the top interconnect tabs overlapping a first edge of the first photovoltaic cell and the bottom interconnect tabs overlapping a second edge of the first photovoltaic cell; and means for assembling the first photovoltaic cell to a second photovoltaic cell by way of the first and second interconnect tabs, the means for affixing being separate from the means for assembling; and the system including means for handling a photovoltaic cell configured to position the first photovoltaic cell in a first position for the affixing of the multiplicities of top and bottom interconnect tabs and in a second position for passing to the means for assembling.

A method, comprising affixing a multiplicity of top interconnect tabs (ribbons) and a multiplicity of bottom interconnect tabs to a first photovoltaic cell, the top interconnect tabs overlapping a first edge of the first photovoltaic cell and the bottom interconnect tabs overlapping a second edge of the first photovoltaic cell; and assembling the first photovoltaic cell to a second photovoltaic cell by way of the first and second interconnect tabs, wherein the first photovoltaic cell is oriented in a first position for the affixing of the top and bottom interconnect tabs and in a second position for assembly to the second photovoltaic cell.

configuring a system for electrically connecting together a multiplicity of photovoltaic cells, said system comprising a transfer arm assembly, comprising a transfer arm that includes means for applying a clamping force between individual ones of said photovoltaic cells and said transfer arm; and an actuator for moving said transfer arm in a vertical plane through an angle greater than or equal to 90 degrees;

moving said transfer arm to a first orientation in which said individual one of said photovoltaic cells is above, and supported by, said transfer arm;

allowing said individual one of said photovoltaic cells to slide along an upper surface of said transfer arm to become positioned against means for locating said individual one of said photovoltaic cells in a second orientation for subsequent processing; and

4. A system for electrically connecting together a multiplicity of photovoltaic cells, comprising:

a wafer transfer system to remove respective, individual photovoltaic cells from said vertical stack of photovoltaic cells contained in said first bin, said wafer transfer system comprising:

a transfer arm assembly, comprising a transfer arm that includes means for applying a clamping force between ones of said respective, individual photovoltaic cells and said transfer arm;

an actuator for moving said transfer arm in a vertical plane through an angle greater than or equal to 90 degrees;

means for optically inspecting said respective, individual photovoltaic cells when supported in an approximately vertical orientation; and

an image processing system electrically connected to said means for optically inspecting and configured to analyze said respective, individual photovoltaic cells for defects.

The system of claim 4. wherein said means for applying a clamping force between said photovoltaic cell and said transfer arm is a vacuum chuck.

The system of claim 4. wherein said means for applying a clamping force comprises an electrostatic chuck.

wherein said turntable is rotatable to position said second bin for loading of defective ones of said respective, individual photovoltaic cells by said transfer arm assembly.

The system of claim 4. further comprising a tabbing subsystem, said tabbing subsystem comprising:

means for locating a plurality of ribbons in alignment with a plurality of corresponding contact areas on said respective, individual photovoltaic cells;

means for soldering each of said plurality of ribbons to corresponding ones of said contact areas on said respective, individual photovoltaic cells.

The system of claim 8. wherein said means for soldering comprises a plurality of soldering heads.

The system of claim 8. further comprising means for applying flux to said ribbons prior to soldering of said ribbons to said corresponding ones of said contact areas.

The system of claim 9. wherein each of said soldering heads is configured to press one of said plurality of ribbons against one of said corresponding contact areas, and wherein said soldering heads simultaneously heat said ribbons to a required soldering temperature.

The system of claim 9. wherein each of said soldering heads is configured to blow gas against a corresponding one of said plurality of ribbons in order to press said corresponding one of said plurality of ribbons against a corresponding one of said contact areas, and wherein said soldering heads simultaneously inductively heat said ribbons to a required soldering temperature.

The system of claim 9. wherein each of said soldering heads is configured with a multiplicity of individually controlled heater elements.

The system of claim 13. wherein each of said individually controlled heater elements is excitable in a timed sequence.

A method for electrically connecting together a pair of photovoltaic cells, said pair comprising a first cell and a second cell, said method comprising the steps of:

configuring said first cell with a first plurality of ribbons on a front side of said first cell, wherein said first plurality of ribbons makes electrical contact with contact areas on said front side of said first cell;

configuring said second cell with a second plurality of ribbons on a back side of said second cell, wherein said second plurality of ribbons makes electrical contact with contact areas on said back side of said second cell, and wherein an end of each of said second plurality of ribbons wraps around an edge of said second cell and is affixed to a front surface of said second cell, near said edge of said second cell;

supporting said first and second cells in an approximately coplanar configuration, with a separation between neighboring sides of said first and second cells;

positioning an end of each ribbon from said first plurality of ribbons above an end of each ribbon from said second plurality of ribbons at said location where said ribbon from said second plurality of ribbons is affixed to said front surface of said second cell; and

joining corresponding ends of said ribbons from said first and second pluralities of ribbons together.

The method of claim 15. wherein said joining comprises spot welding together said corresponding ends of said ribbons from said first and second pluralities of ribbons.

The method of claim 15. wherein said joining comprises soldering together said corresponding ends of said ribbons from said first and second pluralities of ribbons.

A method for electrically connecting together a pair of photovoltaic cells, said pair comprising a first cell and a second cell, said method comprising the steps of:

supporting said pair of photovoltaic cells in an approximately coplanar configuration, with a gap between neighboring sides of said pair of photovoltaic cells;

orienting each of said pair of photovoltaic cells to position an end of a corresponding one of said first plurality of ribbons approximately above an end of a corresponding one of said second plurality of ribbons within said gap between said neighboring sides of said pair of photovoltaic cells;

configuring a pair of joining heads to move along an axis of motion, wherein said axis of motion is approximately perpendicular to said pair of photovoltaic cells, and said axis of motion passes through said gap between said neighboring sides of said pair of photovoltaic cells, such that said pair of joining heads clamps said end of said corresponding one of said first plurality of ribbons against said end of said corresponding one of said second plurality of ribbons; and

joining said corresponding one of said first plurality of ribbons to said end of said corresponding one of said second plurality of ribbons using said joining heads.

The method of claim 18. wherein said joining heads comprise spot welding heads, and said joining comprises spot welding of said end of said corresponding one of said first plurality of ribbons to said end of said corresponding one of said second plurality of ribbons.

The method of claim 18. wherein said joining heads comprise soldering heads, and said joining comprises heating said soldering heads to solder said end of said corresponding one of said first plurality of ribbons to said end of said corresponding one of said second plurality of ribbons

A method for electrically connecting together a pair of photovoltaic cells, said pair comprising a first cell and a second cell, comprising the steps of:

configuring said second cell with a second plurality of ribbons on a back side of said second cell, wherein:

said second plurality of ribbons makes electrical contact with contact areas on said back side of said second cell;

said second cell further comprises an array of vias extending from a front surface to a back surface of said second cell; and

said array of vias is in electrical contact with said second plurality of ribbons on said back side of said second cell;

supporting said pair of photovoltaic cells in an approximately coplanar configuration, with a gap between neighboring sides of said pair of photovoltaic cells;

positioning a corresponding end of each ribbon from said first plurality of ribbons above a corresponding one of said array of vias on said second photovoltaic cell; and

joining each said corresponding end of said ribbons from said first plurality of ribbons to said corresponding one of said array of vias on said second photovoltaic cell.

The method of claim 21. wherein said joining comprises spot welding each said corresponding end of said ribbons from said first plurality of ribbons to said corresponding one of said array of vias on said second photovoltaic cell.

The method of claim 21. wherein said joining comprises soldering each said corresponding end of said ribbons from said first plurality of ribbons to said corresponding one of said array of vias on said second photovoltaic cell.

A method of stringing a pair of photovoltaic cells together, said pair comprising a first cell and a second cell, said method comprising the steps of:

orienting each of said pair of photovoltaic cells to position a corresponding one of said first plurality of ribbons approximately above a corresponding one of said second plurality of ribbons; and

electrically connecting together each said corresponding one of said first plurality of ribbons to said corresponding one of said second plurality of ribbons.

configuring a system for electrically connecting together a multiplicity of photovoltaic cells, said comprising a transfer arm assembly having a transfer arm with means for applying a clamping force between said photovoltaic cell and said transfer arm; a first actuator for moving said transfer arm through an angle in a vertical plane greater than or equal to 90 degrees; a second actuator for moving said transfer arm along an axis perpendicular to said vertical plane; a third actuator for moving said transfer arm radially within said vertical plane; means for optically inspecting said photovoltaic cell when supported in an inspection orientation; and an image processing system electrically connected to said means for optically inspecting, wherein said image processing system is configured to analyze said photovoltaic cell for defects;

inspecting said photovoltaic cell and determining relative locations of a plurality of alignment marks on said photovoltaic cell relative to said transfer arm; and

moving said photovoltaic cell on said transfer arm by means of said second and third actuators to a predetermined position relative to said transfer arm.

US12/477,723 2008-06-03 2009-06-03 System for simultaneous tabbing and stringing of solar cells Abandoned US20100037932A1 ( en )

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System for simultaneous tabbing and stringing of solar cells

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US12/477,723 US20100037932A1 ( en )	2008-06-03	2009-06-03	System for simultaneous tabbing and stringing of solar cells

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System for simultaneous tabbing and stringing of solar cells