How Are Solar Panels Made? What Solar Panels Are Made of How They Are Manufactured
Solar energy’s popularity has rapidly increased in the last several years, making a significant impact on the energy market. According to the Solar Energy Industries Association, the U.S. has installed enough solar to power 13.1 million homes and total U.S. solar capacity is projected to more than double by 2024.
As solar energy use becomes more prevalent, so does information about how it’s harnessed and used. Photovoltaic, or solar, panels can often be found in both commercial and residential areas. How are these panels made, and what materials are used to manufacture them?
The table below outlines the raw materials and parts comprising a solar panel.
Silicon is the basic material for conductive electrical components. Before it can be used, it must undergo a treatment process that removes impurities and converts it to pure silicon, or polysilicon. The industry shouldn’t face material shortages any time soon; silicon is abundant, making up one-quarter of the earth’s crust by weight.
Once the silicon is rid of impurities, it is turned into ingots, which are pure silicon cylinders. The ingots are made from a crystal of silicon that is dipped into polycrystalline silicon. The impurities remain in the melted liquid, so the ingot forms as a completely pure cylinder. From there, the ingot is sliced into.5-millimeter-thick wafers, which are shaped into rectangular or hexagonal shapes so they can fit tightly together.
Boron and phosphorus are added to the wafers through a doping process. The wafers are heated in order to allow atoms from these elements, or dopants, to enter the silicon. When these elements are added to the polysilicon, the first result is an excess of electrons, which is then followed by a deficiency of them. This allows the polysilicon to act as a semiconductor.
To conduct a large amount of electricity, many cells must be connected together by electrical contacts. The group is then connected to the receiver. An anti-reflective coating is applied to the panel to prevent loss of sunlight and wasted energy. The cells are then sealed into a rubber or vinyl acetate, framed in aluminum and covered in glass or plastic.
Silicon: Raw Material in Solar Cells
Silicon is the second most common element in the earth’s crust. According to the Minerals Education Coalition, it isn’t found pure in nature; rather, it’s found combined with oxygen in rocks such as obsidian, granite, and sandstone, in a form known as silica. Silicon can be mined from quartzite, mica, and talc, but sand is its most abundant ore source. The silicon in solar panels is manufactured through a reduction process in which the silica is heated with a carbon material and the oxygen is removed, leaving behind purer, metallurgical-grade silicon.
From there, the grade must be further purified into polysilicon, the solar-grade purity of which is 99.999 percent. To yield polysilicons of different grades, several processes may be applied to the element. For electronic-grade polysilicon, which has a higher purity percentage, the metallurgical-grade silicone must pass through hydrogen chloride at extremely high temperatures and undergo distillation. But to yield a solar-grade end product, the silicone goes through a chemical refinement process. In this process, gases are passed through melted silicon to remove impurities such as boron and phosphorus. In its pure form, solar-grade silicon is then turned into cylinders called ingots, which are then sliced into the small conductive pieces that absorb the sunlight in solar panels.
Ingots Wafers: The Backbone of Solar Cells
Several types of wafers are cut from the ingots: monocrystalline, polycrystalline and silicon ribbons. They differ in terms of their efficiency in conducting sunlight and the amounts of waste they produce.
Monocrystalline wafers are thinly cut from a cylindrical ingot that has a single-crystal structure, meaning that it is comprised of a pure, uniform crystal of silicon. A diamond saw is used to cut the wafers off the cylinder, resulting in a circular shape. However, since circles don’t fit tightly together, the circular wafers are further cut into rectangle or hexagonal shapes, resulting in wasted silicon from the pieces that are removed. According to GreenRhinoEnergy.com, this wasted silicon can be recycled into polysilicon and recut. Researchers are trying to find ways to create monocrystalline cells without so much cutting and waste.
Polycrystalline, sometimes called multicrystalline, ingots are made of multiple crystal structures. They may produce less waste, but they are not as efficient as monocrystalline. The ingots are cube-shaped because they are made from melted silicon poured into a shaped cast. This means the wafers can be cut directly into the desired shape, creating less waste.
Silicon ribbons are thin sheets of multicrystalline silicon. They are so thin that they don’t have to be sliced into wafers. While the thin sheets, or thin films, are flexible, can be used in interesting ways and are less expensive to manufacture, they’re not as durable as wafers and they require more support than other solar panel structures.
Solar Cells: Adding Dopants to Activate the Wafer
While the silicon wafers are complete at this point, they won’t conduct any energy until they go through the doping process. This process involves the ionization of the wafers and the creation of a positive-negative (p-n) junction. The wafers are heated in cylinders at a very high temperature and put into water. Then the top layer of the cylinder is exposed to phosphorus (a negative electrical orientation) while the bottom layer is exposed to boron (a positive electrical orientation). The positive-negative junction of the cell allows it to function properly in the solar panel.
After this step, only a few more things need to happen in order to create a functioning cell. Because silicon naturally reflects sunlight, there is a considerable risk of losing much of the potential energy from the sun that the cells are supposed to absorb. To minimize this reflection, manufacturers coat the cells with antireflective silicon nitride, which gives the cells the final blue color we see in installed panels.
From there, manufacturers implement a system for collecting and distributing the solar energy. This is done through a silk-screen or screen-printing process in which metals are printed on both sides of the cell. These metals make a roadmap for the energy to travel through on its way to the receiver.
Solar Panels: Assembling Cells Into Useful Devices
Solar panel manufacturers employ different proprietary processes to produce their final solar panel products. But, in general, this is an automated process in which robots do the work. First, the cells must be put together to form a big sheet. According to Solar World, a leading manufacturer of solar panels, its process involves soldering six strings of ten cells each, making a rectangle of 60 cells. Each rectangular matrix is laminated onto glass and quickly becomes a larger panel. From there, the panel needs to be framed so that it is sturdy and protected from any weather it will endure.
In addition, the framing must house the electrical equipment that links the panels together and receives the energy.
Where Does Polysilicon Come From?
Polysilicon has one origin: silica. Silica is mined from the earth and is found in sand, rock, and quartz. Because silica has a dioxide component, it must be taken to a plant, where it is converted to silicon through a heating process. According to the United States Geological Society, there are six domestic companies that produce silicon materials at eight plants. These are all located east of the Mississippi River. Imported silicon comes from all around the world, including China, Russia, Japan, Brazil, South Africa, Canada, Australia, and others.
Comprehensive Guide to Solar Panel Types
The push for renewable energy sources has led to a surge in solar energy use. In the past decade alone, the solar industry grew by almost 50%, buoyed by federal support such as the Solar Investment Tax Credit and strong commercial and industrial demand for clean energy.
As the solar sector continues to rise, it’s worth studying the backbone of the solar industry: solar panels.
This guide will illustrate the different types of solar panels available on the market today, their strengths and weaknesses, and which is best suited for specific use cases.
What is a Solar Panel?
Solar panels are used to collect solar energy from the sun and convert it into electricity.
The typical solar panel is composed of individual solar cells, each of which is made from layers of silicon, boron and phosphorus. The boron layer provides the positive charge, the phosphorus layer provides the negative charge, and the silicon wafer acts as the semiconductor.
When the sun’s photons strike the surface of the panel, it knocks out electrons from the silicon “sandwich” and into the electric field generated by the solar cells. This results in a directional current, which is then harnessed into usable power.
The entire process is called the photovoltaic effect, which is why solar panels are also known as photovoltaic panels or PV panels. A typical solar panel contains 60, 72 or 90 individual solar cells.
The 4 Main Types of Solar Panels
There are 4 major types of solar panels available on the market today: monocrystalline, polycrystalline, PERC, and thin-film panels.
Monocrystalline solar panels
Also known as single-crystal panels, these are made from a single pure silicon crystal that is cut into several wafers. Since they are made from pure silicon, they can be readily identified by their dark black color. The use of pure silicon also makes monocrystalline panels the most space-efficient and longest-lasting among all three solar panel types.
However, this comes at a cost — a lot of silicon is wasted to produce one monocrystalline cell, sometimes reaching over 50%. This results in a hefty price tag.
Polycrystalline solar panels
As the name implies, these come from different silicon crystals instead of one. The silicon fragments are melted and poured into a square mold. This makes polycrystalline cells much more affordable since there is hardly any wastage, and gives them that characteristic square shape.
However, this also makes them less efficient in terms of energy conversion and space, since their silicon purity and construction are lower than monocrystalline panels. They also have lower heat tolerance, which means they are less efficient in high-temperature environments.
Passivated Emitter and Rear Cell (PERC) panels
PERC solar panels are an improvement of the traditional monocrystalline cell. This relatively new technology adds a passivation layer in the rear surface of the cell that enhances efficiency in several ways:
- It reflects light back into the cell, increasing the amount of solar radiation that gets absorbed.
- It reduces the natural tendency of electrons to recombine and inhibit the flow of electrons in the system.
- It allows greater wavelengths of light to be reflected. Light waves over 1,180nm can’t be absorbed by silicon wafers and simply pass through, so they end up heating the cell’s metal back sheet and reduce its efficiency. The passivation layer reflects these higher wavelengths and stops them from heating up the back sheet.
PERC panels allow greater solar energy collection in a smaller physical footprint, which makes them ideal for limited spaces. They are only slightly more expensive to produce than traditional panels, due to the added materials needed, but they can be manufactured on the same equipment, and can end up having a lower average cost per watt due to their efficiency.
To get a better feel for the benefits of PERC panels, check out our blog 5 Important Benefits of PERC Solar Panels You Need to Know.
Thin-film solar panels
Thin-film panels are characterized by very fine layers that are thin enough to be flexible. Each panel does not require a frame backing, making them lighter and easier to install. Unlike crystalline silicon panels that come in standardized sizes of 60, 72, and 96-cell counts, thin-film panels can come in different sizes to suit specific needs. However, they are less efficient than typical silicon solar panels.
Thin-Film Solar Panel Variations
Unlike crystalline panels that use silicon, thin-film solar panels are made from different materials. These are:
- Cadmium telluride (CdTe)
- Amorphous silicon (a-Si)
- Copper indium gallium selenide (CIGS)
Cadmium telluride (CdTe)
CdTe has the same low-cost advantage as polycrystalline cells while possessing the lowest carbon footprint, water requirement, and energy payback time of all solar panels types. However, the toxic nature of cadmium makes recycling more expensive than other materials.
Amorphous silicon (a-Si)
Amorphous silicon panels (A-Si) derive their name from their shapeless nature. Unlike mono-and polycrystalline solar cells, the silicon is not structured on the molecular level.
On average, an a-Si cell requires only a fraction of the silicon needed to produce typical silicon cells. This allows them to have the lowest production cost, at the expense of efficiency. This is why a-Si panels are suited for applications that require very little power, such as calculators.
Copper indium gallium selenide (CIGS)
CIGS panels use a thin layer of copper, indium, gallium, and selenium deposited on a glass or plastic backing. The combination of these elements results in the highest efficiency among thin-panel types, though still not as efficient as crystalline silicon panels.
Solar Panel Types by Efficiency
Among all panel types, crystalline solar panels have the highest efficiency.
- Monocrystalline panels have an efficiency rating over 20%.
- PERC panels add an extra 5% efficiency thanks to their passivation layer.
- Polycrystalline panels hover somewhere between 15-17%.
In contrast, thin-film panels are usually 2-3% less efficient than crystalline silicon. On average:
- CIGS panels have an efficiency range of 13-15%.
- CdTe ranges between 9-11%.
- a-Si have the lowest efficiency at 6-8%.
Solar Panel Types by Power Capacity
Monocrystalline cells have the highest power capacity, thanks to their single-crystal construction that allows a higher output rating in a smaller package. Most monocrystalline panels can generate up to 300w of power capacity.
Recent advances in solar technology have allowed polycrystalline panels to bridge the gap. A standard 60-cell polycrystalline panel is now capable of producing between 240-300w. However, monocrystalline panels still beat polycrystalline in terms of power capacity per cell.
Because thin-film panels don’t come in uniform sizes, there is no standard measure of power capacity, and the capacity of one thin-film panel will differ from another based on its physical size. In general, given the same physical footprint, conventional crystalline panels output more power than a thin-film panel of the same size.
Solar Panel Types by Cost
Monocrystalline panels (or modules as they are technically known) carry a hefty price tag, due to its energy-intensive and inefficient manufacturing process with only a 50% yield for every silicon crystal.
Polycrystalline modules are cheaper because they make use of the crystal fragments leftover from monocrystalline production, which results in a simpler manufacturing process and lower production costs.
Among thin-film solar panels, CIGS is the most expensive, followed by CdTe and amorphous silicon. Apart from the lower acquisition cost, thin-film modules can be easier to install thanks to their lighter weight and flexibility, which lowers the cost of labor.
While the total cost of residential systems has declined by more than 65% over the last decade, the soft cost of a system has actually risen from 58% of total system cost in 2014 to 65% in 2020.
For more information about soft costs, check out our article on the soft costs in the solar industry. and what’s being done to reduce them.
|Panel (Module) type||Average Cost per Watt|
|Monocrystalline||1 – 1.50|
|Polycrystalline||0.70 – 1|
|Copper indium gallium selenide (CIGS)||0.60 – 0.70|
|Cadmium telluride (CdTe)||0.50 – 0.60|
|Amorphous silicon (a-Si)||0.43 – 0.50|
Note that these figures don’t include the cost of installation and labor. With labor and other overhead factors, the total can rise to 2.50 to 3.50 per watt.
Other Factors to Consider
The temperature of a solar panel can affect its ability to generate energy. This loss of output is reflected through the temperature coefficient, which is a measure of the panel’s decrease in power output for every 1°C rise over 25°C (77°F).
Monocrystalline and polycrystalline panels have a temperature coefficient between.0.3% / °C to.0.5% / °C, while thin-film panels are closer to.0.2% / °C. This means that thin-film panels can be a good option for hotter environments or places that experience more sunlight throughout the year.
The updated International Building Code of 2012 requires solar panels to match the fire rating of the roof where they are installed. This is to ensure that the modules do not accelerate the spread of flames in the event of a fire. (California goes one step further by requiring the whole PV system, which includes the racking system, to have the same fire rating).
As such, solar panels now carry the same classification rating as roofs:
- effective against severe fire test exposure
- flame spread should not exceed 6 feet
- required for wildland-urban interface areas, or areas with high fire severity and wildfire risk
UL 1703 and UL 61703 standards address hail storms, by dropping 2-inch solid steel spheres on solar panels from a height of 51 inches, and by firing 1-inch ice balls on PV panels with a pneumatic cannon to simulate hail impacts.
Because of their thicker construction, crystalline panels can withstand hail hitting at speeds of up to 50mph, while thin-film solar panels carry a lower rating due to their thin and flexible nature.
While there is no formal solar classification rating for hurricanes, the Department of Energy recently expanded its recommended design specifications for solar panels to safeguard against severe weather.
The new recommendations include:
- Modules with the highest ASTM E1830-15 rating for snow and wind loading in both the front and back.
- Fasteners with true locking capability based on DIN 65151 standard
- The use of through-bolting modules with locking fasteners instead of clamping fasteners
- The use of 3-frame rail systems for improved rigidity and support against twisting
- Tubular frames over open-shaped C channels
- Perimeter fencing around PV systems to slow down wind forces
Light-Induced Degradation (LID)
LID is a performance loss commonly seen in crystalline panels during the first few hours of sun exposure. This happens when sunlight reacts with oxygen traces left over from the manufacturing process, which affects the silicon lattice structure.
The LID loss is directly tied to the manufacturing quality and can range from 1-3%.
Summary: Solar Panel Types Compared
|Initial Cost||Highest||High||Middle||Highest to lowest:|
So, Which Solar Panel Type Should You Use?
As crystalline and thin-film panels have their own pros and cons, the choice of solar panel ultimately comes down to your specific property and condition settings.
Those living in a dense area with limited space should opt for highly efficient monocrystalline modules to make the most of the physical space and maximize utility savings. If budget permits, going for PERC panels can lower energy generation costs even more in the long run.
Those with a sufficiently larger property can save on upfront costs by using polycrystalline solar panels, where a bigger panel footprint can offset the lower panel efficiency. However, a larger footprint could also mean added labor costs, so it’s not necessarily cheaper to get a higher quantity of less expensive panels. While the initial cost may be low, it may eventually be offset by reduced efficiency and higher operating expenses in the long term.
As for thin-film solar panels, these are best suited for locations where the heavy and labor-intensive installation of crystalline silicon is not feasible. Such locations can include commercial buildings with tight spaces or thin roofs; compact spaces such as recreational vehicles and watercraft; and areas that require flexible installation instead of rigid paneling.
Keep in mind that solar panels are designed for long-term installation, which can be as long as 25 years. So whatever type you choose to go with, make sure to do your homework to ensure that it’s the best option for your needs.
New silicon solar cells
The most widely used technology for solar panels is crystalline silicon. It has been in existence for more than 50 years and has a global market share of 95%. than half of all solar panels worldwide contain TNO technology. The energy yield of mass-produced silicon solar cells has risen sharply in the last decade, to well over 20%.
Silicon is derived from the Latin word silex, meaning flint. It used to be called ‘silicium’, with the ‘-ium’ ending because it resembles a metal.
The world’s newest technology
The highest efficiency achieved with a silicon-based solar cell is more than 26%, which is already close to the theoretical maximum. Together with our partners, we want to get as close as possible to this maximum, through new developments and applications. To be precise, by applying the very best functional layers to the silicon wafer and thus making complete solar cells. These are ultra-thin layers down to a few thousandths of a micrometre (nanometre) thin, which are needed for the perfect solar cell and yet can be made industrially. We’re developing this technology in our solar lab, together with companies and other knowledge institutions. We lead the field worldwide in this research.
TNO has always been at the forefront of developing and marketing solar cell and panel technology. The technology for high-efficiency n-type solar cells has already been embraced by a major manufacturer in its so-called PANDA modules. These are based on technology that we developed together with Dutch suppliers.
The global solar energy market is highly competitive. Mass production of solar panels is mainly based in low-wage countries in Asia. The Netherlands is distinguished by its Smart innovations in the preproduction phase. Together with Dutch companies, we develop technologies that they incorporate into materials, components, and production equipment. The aim is to launch these on the market, to strengthen and improve European production of solar panels. In this way, we provide cost-effective and reliable ways to generate solar energy with a high efficiency.
Webinar on solar energy technology
Discover more about solar energy and current technological developments in the webinar ‘Innovations in solar energy technology’.
What is the Difference between Thin-Film and Crystalline Silicon Solar Panel
The two main types of solar panel technology are thin-film and crystalline silicon. Both technologies have advantages and disadvantages, so it’s important to understand the differences before investing in a system.
In this guide, we will compare thin-film and crystalline silicon solar panels to help inform your decision.
What are Thin Film Solar Panels?
Thin-film solar panels are photovoltaic (PV) solar cells constructed of thin layers of a semiconductor material such as amorphous silicon, cadmium telluride, or copper indium gallium selenide.
They are created using the deposition process wherein the thin semiconductor layers are put onto a substrate material such as glass or metal, electrically linked and sealed to shield them from environmental elements.
Thin-film solar panels are lighter, thinner, and more flexible than traditional solar panels, making it easier for them to carry and install. They are also less expensive than standard solar panels due to the less complex production process.
They are more durable than crystalline panels because they have lower temperature coefficients. However, they are not as efficient at converting sunlight into electricity, with light-to-voltage conversion efficiency between 10 and 15%.
What are Thin Film Solar Panels Used For?
Thin film panels are an excellent solution for residential houses and businesses. The panels are easy to place on rooftops, walls, or other surfaces, making them an excellent choice for anyone looking for a simple, cost-effective solution to create electricity.
Thin film panels with high energy efficiency ratings are also commonly used in large-scale solar power projects and battery storage systems. Another potential use for thin-film solar cell panels is solar blinds because they can be folded and stored when not in use.
What are Crystalline Silicon Solar Panels?
Crystalline solar panels, which have been used for decades, are the most efficient and widely used type of solar panel on the market. These solar panels are produced via “crystallization,” creating a single crystal silicon bar in a high-temperature oven. The silicon ingot is then sliced into thin wafers and assembled into a circuit.
Crystalline Solar panels have greater efficiency ratings than thin-film competitors, which means they can convert more of the sun’s energy into usable power. They have a greater voltage rating but are more expensive due to the intricate production process. However, they are becoming more affordable as the price of silicon falls.
What are Crystalline Silicon Solar Panels Used For?
Crystalline panels are the most common type of solar panel used in residential and commercial applications due to their higher efficiency and reliability. These solar panels can power nearly anything you can think of.
They are used in homes to create energy for a household’s electricity demands and in commercial settings to power factories and office buildings. They can also be used in concentrated solar power plants to collect, convert, and send power to the electric grid. Other uses include powering food trucks, electric vehicles, satellite space, etc.
The Difference between Crystalline Silicon and Thin Film Solar Panels
Thin film and crystalline solar panels differ in cost, efficiency, size, etc. Here’s the breakdown: