[Comparison] Monocrystalline vs Polycrystalline Solar Panels
Solar panel technology has dramatically improved over the years, and a range of innovative solar panels are now being introduced in the market. However, when you evaluate your solar panel choices for your PV system, you will come across two major categories of panels: monocrystalline solar panels and polycrystalline solar panels. Both these are conventional options that have been in use for decades. Both types of panels harness sun’s energy, but you must consider the differences between monocrystalline vs polycrystalline solar panels objectively before making your buying decision.
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What are monocrystalline and polycrystalline solar panels?
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Monocrystalline Solar Panels
When you look for monocrystalline panels for sale, you will find them positioned as a relatively premium solar product. Monocrystalline solar panel manufacturers highlight the superior aesthetics as well as efficiency of this panel to convince customers. SunPower monocrystalline panels and LG monocrystalline panels are two of the popular models in this category.
Solar cells for monocrystalline panels are produced with silicon wafers (the silicon is first formed into bars and then it is sliced into thin wafers). The panel derives its name “mono” because it uses single-crystal silicon. As the cell is constituted of a single crystal, it provides the electrons more space to move for a better electricity flow. This is the reason behind the higher efficiency of monocrystalline vs. polycrystalline solar panels.
Polycrystalline Solar Panels
The efficiency of polycrystalline solar panels is somewhat lower, but the benefit for customers is that this option is more affordable. In addition, when you seek polycrystalline solar panels for sale, the sellers may highlight the blue hue of these panels compared to the monocrystalline panels’ black hue.
Although polycrystalline solar panels are also composed of silicon, it does not involve the use of single-crystal silicon. Polycrystalline solar panel manufacturers melt multiple silicon fragments together to produce the wafers for these panels. For this reason, they are called “poly” or multi crystalline. The electrons in each cell will have less space to move because of many crystals in a cell. Therefore, the efficiency ratings of polycrystalline solar panels are relatively lower.
Comparison chart: Monocrystalline vs. Polycrystalline solar panels
To choose between the best monocrystalline solar panels and best polycrystalline solar panels, you should evaluate them on the following parameters:
Price
Monocrystalline solar panels for sale will be relatively more costly compared to polycrystalline solar panels for sale. You should draw a careful cost-benefit analysis and determine your budget in order to make the right choice for you.
Efficiency
These products are made from superior grade silicone, which has a single-crystal structure. Therefore, electricity flow has minimal resistance in these cells. On the other hand, although one of the advantages of polycrystalline solar panels is their lower price, but their efficiency is also lower (between 14 and 16 percent) due to their reduced silicon purity.
Lifespan
When you compare the initial installation costs between monocrystalline vs. polycrystalline solar panels, you should also look at the average lifespan of each. Monocrystalline solar panel manufacturers will usually offer a 25-year warranty because of the longer lifespan of the product. On this parameter of lifespan, polycrystalline solar panels are not very different, but the warranty period offered by the manufacturers may vary.
Temperature Coefficient
In warm weather, monocrystalline solar panels can deliver higher efficiency because of their higher temperature coefficient. The output degradation in monocrystalline panels is lower as the temperature rises. If you are living in a region where the summers are longer and warmer, you should carefully consider the temperature coefficient of the solar panels you are choosing.
Aesthetics
Attractive physical appearance of the solar panels depends on an individual’s personal sense of aesthetics. But many users find that the speckled blue hue of polycrystalline silicon is not too easy on the eyes. Therefore, they may prefer monocrystalline solar panels as they find them more uniform in appearance, and thus more aesthetically desirable.
Monocrystalline or polycrystalline panels: Which one is right for you?
Once you have considered the pros of monocrystalline solar panels versus the pros of polycrystalline solar panels, it gets easier to make your decision. But don’t FOCUS only on the pros, and also dispassionately evaluate the cons of monocrystalline solar panels versus the cons of polycrystalline solar panels. In addition, the following considerations should help you determine which one is the right choice for you:
Individual Preferences
If the color of your solar roof matters to you, you should know that monocrystalline vs. polycrystalline solar panels will appear somewhat differently in terms of color. The typical polycrystalline panel will have a bluer shade, while the monocrystalline panel will be darker (black) in color.
If you have a personal preference for a particular solar panel manufacturer, you should consider whether they are more popularly known for their poly or mono solar panels.
Space Limitations
If the available space on your roof is limited but you have a need for more solar output, you may consider monocrystalline solar panels because of their higher efficiency. It is worth paying the additional cost for these panels in your situation because you can maximize your power output even within your space constraints to accommodate a PV system.
On the other hand, if you have plenty of free space available on your roof, or you plan to install a ground-mounted PV system, you may consider the more economical choice of polycrystalline solar panels.
Amount of Dust, Snow, and Shade
According to some industry experts, monocrystalline solar panel systems have been known to break down if they are only marginally covered in snow or dust or a part of the panel becomes shaded. Polycrystalline solar panels, on the other hand, are somewhat more resilient in these conditions.
Therefore, if your roof is partially shady, or you live in a region where the climate is snowy or dusty, you might find polycrystalline solar panels to be a more suitable option. If you have a strong preference for monocrystalline solar panels even in this situation, you may consider installing a micro-inverter to counter these issues. However, that will mean an additional investment on hardware.
Climate
As discussed in the earlier sections, the heat tolerance of a monocrystalline solar panel is higher than that of a polycrystalline panel. If you reside in a region that has a hotter climate for better part of the year, this could effectively reduce the lifespan of your panels if you choose the polycrystalline option.
But industry observers tend to agree that the effect would only be minor in the long run, unless you are living in a desert climate. It is best to discuss this issue with your installation company who can guide you better according to the local climate-related facts and data in your region.
Solar Financing
How you plan to finance your PV system might also have a role to place in determining your choice of a solar panel. For instance, if you go for a PPA (power purchase agreement), you will be paying per KWH for the amount of electricity generated by the system.
This would mean that above the type of your PV equipment, your savings will be determined by your monthly payments. On the other hand, if you are purchasing your own PV system, investing in monocrystalline solar panels for their superior efficiency could lead to better returns on your investment.
Overview: Other advanced conventional solar panels and new solar panel technologies
A number of cutting-edge solar panel technologies have been introduced into the market, which are worth considering. You should have a fair understand of these innovative options in order to make the right decision for your solar power system.
Flexible Solar Panels
Although most of the solar panels today are produced from mono or poly solar cells, there is another solar technology known as flexible solar panels. These panels can be produced both as crystalline flexible solar panels and “thin-film” solar panels. Thin-film solar panels are produced by depositing a very thin layer of conductive material over a plastic or glass-based backing plate.
Most of the flexible solar panel technology today is affordable, but less efficient. You may not prefer it for your home if you have space constraints. But where space is not a limitation, flexible solar panels can be a cost-effective option in some cases. These flexible panels are particularly suited for mobile use such as RVs as well as boats when you may not have flat surface available to mount the panel.
PERC Cells
Passivated Emitter and Rear Cell (PERC) technology is another unique option that is gaining acceptance. PERC cells are differentiated by an additional layer of material (the passivation layer) on the solar panel’s backside. Consider this passivation layer as a sort of mirror. It will reflect light that skips through the panel, allowing it a second opportunity to get absorbed by the PV cell.
The higher absorption of radiation results in greater efficiency of the panel. The advantage here is that adding a passivation layer will not significantly increase the cost, and the benefits of efficiency will exceed the additional cost.
Half-Cut Cells
Just as the name suggests, half-cut cells are PV cells cut in half. Compared to the traditional solar cells, the smaller size of these half-cut PV cells provides an advantage in terms of increased efficiency. As the size of these cells is half the size of a conventional solar cell, it will produce about half the electrical current. Reduced current between PV cells means reduced resistance. This is what makes the half-cut cells more efficient.
Half-cut cells also have a relatively higher shade-tolerance. Shade falling on a PV cell not just compromises the cell’s efficiency, but also affects all other cells connected in that series. Based on this you could lose a considerable part of your solar panel’s production. But half-cut cells are wired differently and the production loss because of shading gets minimized.
Bifacial Solar Panels
These are solar panels which contain conductive material on both faces (both sides) of the panel. The aim is to maximize the benefit of reflected sunshine that hits the panel’s backside. The challenge with bifacial solar panels is that the system must be mounted in a raised position to achieve clearance under the array.
The roofing below the array should also have the appropriate reflective material (such as white rocks). For these reasons, the installation of bifacial panels becomes more expensive, and may not justify the gains in efficiency. However, as the technology improves over time, this could change.
Transparent Solar Panels
This is a futuristic solar panel technology that aims to produce solar power from glass Windows in homes and offices. To achieve success with this technology, scientists have created the transparent luminescent solar concentrator (TLSC) which can practically transform any glass window into a solar panel.
The technology has still not reached a commercial stage, but researchers believe that in future these transparent solar panels will be installed in homes and buildings with large glass Windows. Once the conventional glass window is replaced with a transparent solar panel, it can potentially transform every building into a solar power generator without affecting the aesthetics.
PV Shingles
Photovoltaic shingles or solar power shingles are among the most pragmatic and successful innovations that are rapidly gaining in popularity. These solar panels will clone the function and looks of traditional roofing materials, such as asphalt and slate, so you don’t have to compromise on the aesthetics for the sake of generating solar power.
Creative solar roofing options such as solar shingles could significantly increase the value of your home, while delivering you excellent solar output just like the traditional solar roof panels.
Final Word
Your home deserves the best that solar technology offers today at an affordable cost. You can achieve that if you are willing to consider the unique features, suitability and pros and cons of various solar panel options available to you. Draw your own comparison between monocrystalline vs. polycrystalline solar panels as well as other choices to make the right decision for your home. comment
Solar Cells
Solar cells are in fact large area semiconductor diodes. Due to photovoltaic effect energy of light (energy of photons) converts into electrical current. At p-n junction, an electric field is built up which leads to the separation of the charge carriers (electrons and holes). At incidence of photon stream onto semiconductor material the electrons are released, if the energy of photons is sufficient. Contact to a solar cell is realised due to metal contacts. If the circuit is closed, meaning an electrical load is connected, then direct current flows. The energy of photons comes in packages which are called quants. The energy of each quantum depends on the wavelength of the visible light or electromagnetic waves. The electrons are released, however, the electric current flows only if the energy of each quantum is greater than WL. WV (boundaries of valence and conductive bands). The relation between frequency and incident photon energy is as follows:
h. Planck constant (6,626·10.34 Js), μ. frequency (Hz)
Crystalline solar cells
Among all kinds of solar cells we describe silicon solar cells only, for they are the most widely used. Their efficiency is limited due to several factors. The energy of photons decreases at higher wavelengths. The highest wavelength when the energy of photon is still big enough to produce free electrons is 1.15 μm (valid for silicon only). Radiation with higher wavelength causes only heating up of solar cell and does not produce any electrical current. Each photon can cause only production of one electron-hole pair. So even at lower wavelengths many photons do not produce any electron-hole pairs, yet they effect on increasing solar cell temperature. The highest efficiency of silicon solar cell is around 23 %, by some other semi-conductor materials up to 30 %, which is dependent on wavelength and semiconductor material. Self loses are caused by metal contacts on the upper side of a solar cell, solar cell resistance and due to solar radiation reflectance on the upper side (glass) of a solar cell. Crystalline solar cells are usually wafers, about 0.3 mm thick, sawn from Si ingot with diameter of 10 to 15 cm. They generate approximately 35 mA of current per cm 2 area (together up to 2 A/cell) at voltage of 550 mV at full illumination. Lab solar cells have the efficiency of up to 30 %, and classically produced solar cells up to 20 %.
Wafers and crystalline solar cells (courtesy: SolarWorld)
Amorphous solar cells
The efficiency of amorphous solar cells is typically between 6 and 8 %. The Lifetime of amorphous cells is shorter than the lifetime of crystalline cells. Amorphous cells have current density of up to 15 mA/cm 2. and the voltage of the cell without connected load of 0.8 V, which is more compared to crystalline cells. Their spectral response reaches maximum at the wavelengths of blue light therefore, the ideal light source for amorphous solar cells is fluorescent lamp.
Surface of different solar cells as seen through microscope (courtesy: Helmholtz-Zentrum Berlin)
Solar Cell Models
The simplest solar cell model consists of diode and current source connected parallelly. Current source current is directly proportional to the solar radiation. Diode represents PN junction of a solar cell. Equation of ideal solar cell, which represents the ideal solar cell model, is:
IL. light-generated current [1] (A), Is. reverse saturation current [2] (A) (aproximate range 10.8 A/m 2 ) V. diode voltage (V), VT. thermal voltage (see equation below), VT = 25.7 mV at 25°C n. diode ideality factor = 1. 2 (n = 1 for ideal diode)
Thermal voltage VT (V) can be calculated with the following equation:
k. Boltzmann constant = 1.38·10.23 J/K, T. temperature (K) q. charge of electron = 1.6·10.19 As
FIGURE 1: Ideal solar cell model
FIGURE 2: Real Solar cell model with serial and parallel resistance [3] Rs and Rp, internal resistance results in voltage drop and parasitic currents
The working point of the solar cell depends on load and solar irradiation. In the picture, I-V characteristics at short circuit and open circuit conditions can be seen. Very important point in I-U characteristics is Maximum Power Point, MPP. In practice we can seldom reach this point, because at higher solar irradition even the cell temperature increases, and consequently decreasing the output power. Series and paralell parasitic resistances have influence on I-V curve slope. As a measure for solar cell quality fill-factor, FF is used. It can be calculated with the following equation:
IMPP. MPP current (A), VMPP. MPP voltage (V) Isc. short circuit current (A), Voc. open circuit voltage (V)
In the case of ideal solar cell fill-factor is a function of open circuit parameters and can be calculated as follows:
Where voc is normalised Voc voltage (V) calculated with equation below:
k. Boltzmann constant = 1,38·10.23 J/K, T. temperature (K) q. charge of electron = 1,6·10.19 As, n. diode ideality factor (-) Voc. open circuit voltage (V)
For detailed numerical simulations more accurate models, like two diode model, should be used. For additional explanations and further solar cell models description please see literature below.
Solar Cell Characteristics
Samples of solar cell I-V and power characteristics are presented on pictures below. Typical point on solar cell characteristics are open circuit (when no load is connected), short circuit and maximum power point. Presented characteristics were calculated for solar cell with following data: Voc = 0,595 mV, Isc = 4,6 A, IMPP = 4,25 A, VMPP = 0,51 V, and PMPP temperature coefficient γ =.0,005 %/K. Calculation algorithm presented in the book Photovoltaik Engineering (Wagner, see sources) was used.
FIGURE 3: Solar cell I-V characteristics for different irradiation values
FIGURE 4: Solar cell power characteristics for different irradiation values
FIGURE 5: Solar cell I-V characteristics temperature dependency
FIGURE 6: Solar cell power characteristics temperature dependency
| [1] | Sometimes term photocurrent IPh is also used. |
| [2] | Sometimes term dark current Io is also used. |
| [3] | For paralell resistanse term shunt resistor Rsh is also used. |
Simulation Tools
Open Photovoltaics Analysis Platform. Open Photovoltaics Analysis Platform (OPVAP) is a group of software used in the field of solar cells, which include analyzing experimental data, calculating optimum architecture based on your materials, and even some research assistant tools such as PicureProcess.
Organic Photovoltaic Device Model. Organic Photovoltaic Device Model (OPVDM) is a free 1D drift diffusion model specifically designed to simulate bulk-heterojuncton organic solar cells, such as those based on the P3HT:PCBM material system. The model contains both an electrical and an optical solver, enabling both current/voltage characteristics to be simulated as well as the optical modal profile within the device. The model and it’s easy to use graphical interface is available for both Linux and Windows.
Other Technologies. Links
NanoFlex Power. flexible organic solar cells.
sphelar power. spherical solar cells technology.
Global Crystalline Silicon Solar Cell (C Si) Market – Industry Trends and Forecast to 2029
Global Crystalline Silicon Solar Cell (C Si) Market, By Type (Mono-Crystalline, Multi-Crystalline), End User (Residential, Commercial, Utility-Scale). Industry Trends and Forecast to 2029.
Crystalline Silicon Solar Cell (C Si) Market Analysis and Size
The crystalline silicon solar cell market is driven by the high demand of renewable energy and upsurge in the electricity demand. Strict government regulations on carbon emission and limited availability of fossil fuels create the strong need for cost-effective and efficient sources such as solar energy. Crystalline silicon solar cells are highly efficient compared to other alternative technologies, such as non-silicon solar cells and amorphous silicon.
Data Bridge Market Research analyses that the crystalline silicon solar cell (C Si) market was valued at USD 25,294.30 million in 2021 and is expected to reach USD 41,548.53 million by 2029, registering a CAGR of 6.40% during the forecast period of 2022 to 2029. In addition to the insights on market scenarios such as market value, growth rate, segmentation, geographical coverage, and major players, the market reports curated by the Data Bridge Market Research also include in-depth expert analysis, geographically represented company-wise production and capacity, network layouts of distributors and partners, detailed and updated price trend analysis and deficit analysis of supply chain and demand.
Crystalline Silicon Solar Cell (C Si) Market Scope and Segmentation
Report Metric
2020 (Customizable to 2014. 2019)
Revenue in USD million, Volumes in Units, Pricing in USD
Type (Mono-Crystalline, Multi-Crystalline), End User (Residential, Commercial, Utility-Scale)
U.S., Canada and Mexico in North America, Germany, France, U.K., Netherlands, Switzerland, Belgium, Russia, Italy, Spain, Turkey, Rest of Europe in Europe, China, Japan, India, South Korea, Singapore, Malaysia, Australia, Thailand, Indonesia, Philippines, Rest of Asia-Pacific (APAC) in the Asia-Pacific (APAC), Saudi Arabia, U.A.E, South Africa, Egypt, Israel, Rest of Middle East and Africa (MEA) as a part of Middle East and Africa (MEA), Brazil, Argentina and Rest of South America as part of South America
Greatcell Solar (Australia), Exeger Operations AB (Sweden), Fujikura Europe Ltd. (U.K.), G24 Power Ltd. (U.K.), Konica Minolta Sensing Europe B.V. (Netherlands), Merck KGaA (Germany), Oxford PV (U.K.), Peccell Technologies, Inc. (Japan), Sharp Corporation (Japan), Solaronix SA (Switzerland), Sony Corporation (Japan), Ricoh (Japan), First Solar. (US), SunPower Corporation (U.S.), Suniva Inc (U.S.), Tata Power Solar Systems Ltd. (India), SHARP CORPORATION (Japan), ALPS Technology Inc. (U.S.), Solaris Technology Industry, Inc. (India), GREEN BRILLIANCE RENEWABLE ENERGY LLP (India), Trina Solar (China), Canadian Solar. (Canada)
Market Definition
Crystalline silicon solar cell is made up of highly pure silicon wafers which are used to convert solar energy into electrical energy. Crystalline silicon (c-Si) is the crystalline form of silicon. Crystalline silicon is the dominant semiconducting material widely used in photovoltaic technology to manufacture solar cells. These solar cells are assembled into solar panels as part of a photovoltaic system to produce solar power from sunlight.
Crystalline Silicon Solar Cell (C Si) Market Dynamics
The increase in awareness among the market players and buyers regarding the adverse effect of other solar cell on environmental increase the demand of crystalline silicon solar cell (C Si) because it is renewable source-based power. Also, the rise in the dependence on unconventional energy sources has a positive impact on the market, which are expected to drive the market’s growth.
The rise in the number of solar system installation further influence the growth of the crystalline silicon solar cell (C Si) market. The rise in demand for crystalline silicon solar cell (C Si) due to rising need to decline the of solar cell modules are expected to drive the market growth.
over, change in lifestyle, surge in investments, Rapid urbanization and augmented consumer spending positively impact the crystalline silicon solar cell (C Si) market.
Recent technical advancements have reduced the production cost of the crystalline silicon solar cell (C Si), which extends the profitable opportunities to the major market players in the forthcoming period. Furthermore, improvement in infrastructure development activities will further expand the growth of the crystalline silicon solar cell (C Si) market.
over, increasing the number of strategic collaborations and emerging new markets will act as market drivers and increase the beneficial opportunities for the market’s growth rate.
Restraints/ Challenges
However, Due to the negative impact of silicon on the environment, the government has imposed some stringent regulations which are expected obstruct the demand of the crystalline silicon solar cell (C Si) in the market.
The lower productivity of the crystalline silicon solar cell (C Si) compared to other alternatives might be hinder the growth of the crystalline silicon solar cell (C Si) market globally during the forecast period of 2022-2029.
This crystalline silicon solar cell (C Si) market report provides details of new recent developments, trade regulations, import-export analysis, production analysis, value chain optimization, market share, impact of domestic and localized market players, analyses opportunities in terms of emerging revenue s, changes in market regulations, strategic market growth analysis, market size, category market growths, application niches and dominance, product approvals, product launches, geographic expansions, technological innovations in the market. To gain more info on the crystalline silicon solar cell (C Si) market contact Data Bridge Market Research for an Analyst Brief, our team will help you take an informed market decision to achieve market growth.
Impact and Current Market Scenario of Raw Material Shortage and Shipping Delays
Data Bridge Market Research offers a high-level analysis of the market and delivers information by keeping in account the impact and current market environment of raw material shortage and shipping delays. This translates into assessing strategic possibilities, creating effective action plans, and assisting businesses in making important decisions.
Apart from the standard report, we also offer in-depth analysis of the procurement level from forecasted shipping delays, distributor mapping by region, commodity analysis, production analysis, price mapping trends, sourcing, category performance analysis, supply chain risk management solutions, advanced benchmarking, and other services for procurement and strategic support.
COVID-19 Impact on Crystalline Silicon Solar Cell (C Si) Market
The COVID-19 had a negative impact on the crystalline silicon solar cell (C Si) market due to the strict social distancing and lockdowns to contain the widespread of the corona virus. The partial shutdown of the business, economic uncertainty and low consumer confidence has impacted the demand of the crystalline silicon solar cell (C Si) technology. The supply chain got hindered during this pandemic along with the delay logistics activities. However, the crystalline silicon solar cell (C Si) market is anticipated to recover its pace during the post pandemic scenario.
Expected Impact of Economic Slowdown on the Pricing and Availability of Products
When economic activity slows, industries begin to suffer. The forecasted effects of the economic downturn on the pricing and accessibility of the products are taken into account in the market insight reports and intelligence services provided by DBMR. With this, our clients can typically keep one step ahead of their competitors, project their sales and revenue, and estimate their profit and loss expenditures.
Global Crystalline Silicon Solar Cell (C Si) Market Scope
The crystalline silicon solar cell (C Si) market is segmented on the basis of type and end user. The growth amongst these segments will help you analyze meagre growth segments in the industries and provide the users with a valuable market overview and market insights to help them make strategic decisions for identifying core market applications.
Crystalline Silicon Solar Cell Market Regional Analysis/Insights
The crystalline silicon solar cell (C Si) market is analysed and market size insights and trends are provided by country, type and end user as referenced above.
The countries covered in the crystalline silicon solar cell (C Si) market report U.S., Canada and Mexico in North America, Germany, France, U.K., Netherlands, Switzerland, Belgium, Russia, Italy, Spain, Turkey, Rest of Europe in Europe, China, Japan, India, South Korea, Singapore, Malaysia, Australia, Thailand, Indonesia, Philippines, Rest of Asia-Pacific (APAC) in the Asia-Pacific (APAC), Saudi Arabia, U.A.E, South Africa, Egypt, Israel, Rest of Middle East and Africa (MEA) as a part of Middle East and Africa (MEA), Brazil, Argentina and Rest of South America as part of South America
Asia Pacific dominates the crystalline silicon solar cell (C Si) market in terms of market share. This is due to the promotion of solar energy along with the government favourable policies to encourage the solar installation in many sectors of the this region
North America is projected to be the fastest developing region due to the adoption of advanced technology in this region.
The country section of the report also provides individual market impacting factors and changes in market regulation that impact the current and future trends of the market. Data points like down-stream and upstream value chain analysis, technical trends and porter’s five forces analysis, case studies are some of the pointers used to forecast the market scenario for individual countries. Also, the presence and availability of global brands and their challenges faced due to large or scarce competition from local and domestic brands, impact of domestic tariffs and trade routes are considered while providing forecast analysis of the country data.
Competitive Landscape and Crystalline Silicon Solar Cell (C Si) Market Share Analysis
The crystalline silicon solar cell (C Si) market competitive landscape provides details by competitor. Details included are company overview, company financials, revenue generated, market potential, investment in research and development, new market initiatives, global presence, production sites and facilities, production capacities, company strengths and weaknesses, product launch, product width and breadth, application dominance. The above data points provided are only related to the companies’ FOCUS related to crystalline silicon solar cell (C Si) market.
Some of the major players operating in the crystalline silicon solar cell (C Si) market are:
Science and Tech Spotlight: Alternative Materials for Solar Cells
This Spotlight examines evolving solar cell technology. Most electricity-generating solar cells are made with crystalline silicon in a process that is complex, expensive, and energy-intensive. Alternative materials may perform better and be easier and cheaper to make. Some absorb light 10-100 times more efficiently using thin films. In addition, these cells can be manufactured quickly and easily, reducing cost.
Some alternative materials remain in the early stages of research and development but others are already in use. For example, cadmium telluride solar cells are produced commercially and cost about the same as crystalline silicon cells.
Why This Matters
US generation of electricity from solar energy could grow six-fold by 2050. Alternatives to commonly used crystalline silicon cells may reduce material usage, manufacturing capital expenditures, and lifecycle greenhouse gas emissions. Many of these new materials, however, are under development, and more research is needed to better understand their potential.
The Technology
What is it? Most solar cells (the components that generate electricity from sunlight) are currently produced with crystalline silicon in a process that is complex, expensive, and energy-intensive. Alternative materials—such as cadmium telluride, amorphous silicon, perovskites, and organic (carbon-containing) compounds—applied in thin layers of film may perform better and be easier and cheaper to manufacture.
How does it work? As sunlight shines on a solar cell, some of the energy is absorbed to generate electricity either for immediate use or for storage in batteries (see fig. 1). The more readily a given solar cell absorbs light and transforms it into electricity, the higher its efficiency. The electric current generated by sunlight flows through wires that connect the front and back contacts of the solar cell.
Figure 1. A simplified representation of how a solar cell generates an electric current.
Some alternative materials absorb light 10 to 100 times more strongly than crystalline silicon, allowing them to produce electricity using less material. In turn, solar cells made with these materials are typically thinner and weigh less. In addition, these thin film solar cells can be manufactured quickly, reducing cost.
How mature is it? The maturity of these alternative materials varies widely, with some currently used to manufacture solar cells and others in the early stages of research and development. For example, cadmium telluride cells and copper indium gallium diselinide cells together account for roughly 10 percent of current solar cells and they are already cost-competitive with crystalline silicon cells.
Novel solar cells under development use a variety of materials. Among them is amorphous silicon, which is non-crystalline and can be deposited as a thin film. Perovskites are an emerging class of materials with rapidly increasing efficiencies. Organic materials offer yet another option for thin films. They consist of carbon-containing compounds, either long chains or molecules, tailored to absorb specific wavelengths of light. Researchers are also investigating the use of quantum dots—microscopic particles of compounds such as cadmium telluride, cadmium selenide, indium phosphide, or zinc selenide, that are able to produce electricity from light.
Although these diverse materials differ in their chemical composition, they all fall under the category known as thin films because of the extremely thin layer—comparable in thickness to a red blood cell—in which they are applied (see fig. 2). In addition to being easy to produce and relatively inexpensive, these materials can be deposited on a variety of substrates, including flexible plastics in some cases.
Figure 2. Current and potential alternative materials for solar cells are applied in extremely thin layers, with emerging materials being the thinnest.
In addition to absorbing light, solar cells must convert it to electricity. While promising, commercial thin film solar cells currently average a conversion efficiency in the range of 12 to 15 percent, compared to 15 to 21 percent for crystalline silicon, according to a Massachusetts Institute of Technology (MIT) study. In addition, they require appropriate sealing materials to protect them from ambient oxygen and moisture. As a result, many alternative solar cell materials are currently under development or limited to specialized applications.
Challenges
Policy Context and Questions
As alternative materials for solar cells continue to evolve and mature, some key questions that policymakers could consider include:
- What steps could help encourage further development and use of alternative energy sources such as solar cell materials?
- What analyses of incentives and barriers can determine whether government stimulus may be needed for private sector investment in solar cell materials and what are the trade-offs of such a stimulus?
- What actions could help ensure sufficient understanding of the human health and environmental impacts of various solar cell materials across the full lifecycle?
For more information, contact Karen Howard at 202-512-6888 or HowardK@gao.gov.
Types of Solar Panels: Pros and Cons
Emily Rhode is a science writer, communicator, and educator with over 20 years of experience working with students, scientists, and government experts to help make science more accessible and engaging. She holds a B.S. in Environmental Science and an M.Ed. in Secondary Science Education.
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There are three main types of solar panels commercially available: monocrystalline solar panels, polycrystalline solar panels, and thin-film solar panels. There are also several other promising technologies currently in development, including bifacial panels, organic solar cells, concentrator photovoltaics, and even nano-scale innovations like quantum dots.
Each of the different types of solar panels has a unique set of advantages and disadvantages that consumers should consider when choosing a solar panel system.
Monocrystalline solar cells are slower and more expensive to produce than other types of solar cells due to the precise way the silicon ingots must be made. In order to grow a uniform crystal, the temperature of the materials must be kept very high. As a result, a large amount of energy must be used because of the loss of heat from the silicon seed that occurs throughout the manufacturing process. Up to 50% of the material can be wasted during the cutting process, resulting in higher production costs for the manufacturer.
But these types of solar cells maintain their popularity for a number of reasons. First, they have a higher efficiency than any other type of solar cell because they are made of a single crystal, which allows electrons to flow more easily through the cell. Because they are so efficient, they can be smaller than other solar panel systems and still generate the same amount of electricity. They also have the longest life span of any type of solar panel on the market today.
One of the biggest downsides to monocrystalline solar panels is the cost (due to the production process). In addition, they are not as efficient as other types of solar panels in situations where the light does not hit them directly. And if they get covered in dirt, snow, or leaves, or if they are operating in very high temperatures, their efficiency declines even more. While monocrystalline solar panels remain popular, the low cost and rising efficiency of other types of panels are becoming increasingly appealing to consumers.
Polycrystalline Solar Panels
As the name implies, polycrystalline solar panels are made of cells formed from multiple, non-aligned silicon crystals. These first-generation solar cells are produced by melting solar grade silicon and casting it into a mold and allowing it to solidify. The molded silicon is then sliced into wafers to be used in a solar panel.
Polycrystalline solar cells are less expensive to produce than monocrystalline cells because they do not require the time and energy needed to create and cut a single crystal. And while the boundaries created by the grains of the silicon crystals result in barriers for efficient electron flow, they are actually more efficient in low-light conditions than monocrystalline cells and can maintain output when not directly angled at the sun. They end up having about the same overall energy output because of this ability to maintain electricity production in adverse conditions.
The cells of a polycrystalline solar panel are larger than their monocrystalline counterparts, so the panels may take up more space to produce the same amount of electricity. They are also not as durable or long-lasting as other types of panels, although the differences in longevity are small.
Thin-Film Solar Panels
The high cost of producing solar-grade silicon led to the creation of several types of second- and third-generation solar cells known as thin-film semiconductors. Thin-film solar cells need a lower volume of materials, often using a layer of silicon as little as one micron thick, which is about 1/300th of the width of mono- and polycrystalline solar cells. The silicon is also of lower quality than the kind used in monocrystalline wafers.
Many solar cells are made from non-crystalline amorphous silicon. Because amorphous silicon does not have the semiconductive properties of crystalline silicon, it must be combined with hydrogen in order to conduct electricity. Amorphous silicon solar cells are the most common type of thin-film cell, and they are often found in electronics like calculators and watches.
Other commercially viable thin-film semiconductor materials include cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and gallium arsenide (GaAs). A layer of semiconductor material is deposited on an inexpensive substrate like glass, metal, or plastic, making it cheaper and more adaptable than other solar cells. The absorption rates of the semiconductor materials are high, which is one of the reasons they use less material than other cells.
Production of thin-film cells is much simpler and faster than first-generation solar cells, and there are a variety of techniques that can be used to make them, depending on the capabilities of the manufacturer. Thin-film solar cells like CIGS can be deposited on plastic, which significantly reduces its weight and increases its flexibility. CdTe holds the distinction of being the only thin film that has lower costs, higher payback time, lower carbon footprint, and lower water use over its lifetime than all other solar technologies.
However, the downsides of thin-film solar cells in their current form are numerous. The cadmium in CdTe cells is highly toxic if inhaled or ingested, and can leach into the ground or water supply if not properly handled during disposal. This could be avoided if the panels are recycled, but the technology is currently not as widely available as it needs to be. The use of rare metals like those found in CIGS, CdTe, and GaAs can also be an expensive and potentially limiting factor in producing large amounts of thin-film solar cells.
Other Types
The variety of solar panels is much greater than what is currently on the commercial market. Many newer types of solar technology are in development, and older types are being studied for possible increases in efficiency and decreases in cost. Several of these emerging technologies are in the pilot phase of testing, while others remain proven only in laboratory settings. Here are some of the other types of solar panels that have been developed.
Bifacial Solar Panels
Traditional solar panels only have solar cells on one side of the panel. Bifacial solar panels have solar cells built on both sides in order to allow them to collect not only incoming sunlight, but also albedo, or reflected light off the ground beneath them. They also move with the sun in order to maximize the amount of time that sunlight can be collected on either side of the panel. A study from the National Renewable Energy Laboratory showed a 9% increase in efficiency over single-sided panels.
Concentrator Photovoltaic Technology
Concentrator photovoltaic technology (CPV) uses optical equipment and techniques such as curved mirrors to concentrate solar energy in a cost-efficient way. Because these panels concentrate sunlight, they do not need as many solar cells to produce an equal amount of electricity. This means that these solar panels can use higher quality solar cells at a lower overall cost.
Organic Photovoltaics
Organic photovoltaic cells use small organic molecules or layers of organic polymers to conduct electricity. These cells are lightweight, flexible, and have a lower overall cost and environmental impact than many other types of solar cells.
Perovskite Cells
The Perovskite crystalline structure of the light-collecting material gives these cells their name. They are low cost, easy to manufacture, and have a high absorbance. They are currently too unstable for large-scale use.
Dye-Sensitized Solar Cells (DSSC)
These five-layered thin-film cells use a special sensitizing dye to help the flow of electrons which creates the current to produce electricity. DSSC have the advantage of working in low light conditions and increasing efficiency as temperatures rise, but some of the chemicals they contain will freeze at low temperatures, which makes the unit inoperable in such situations.
Quantum Dots
This technology has only been tested in laboratories, but it has shown several positive attributes. Quantum dot cells are made from different metals and work on the nano-scale, so their power production-to-weight ratio is very good. Unfortunately, they can also be highly toxic to people and the environment if not handled and disposed of properly.
Almost all solar panels sold commercially are monocrystalline, common because they’re so compact, efficient, and long-lasting. Monocrystalline solar panels are also proven to be more durable under high temperatures.
Monocrystalline solar panels are the most efficient, with ratings ranging from 17% to 25%. In general, the more aligned the silicon molecules of a solar panel are, the better the panel will be at converting solar energy. The monocrystalline variety has the most aligned molecules because it’s cut from a single source of silicon.
Thin-film solar panels tend to be the cheapest of the three commercially available options. This is because they’re easier to manufacture and require less materials. However, they also tend to be the least efficient.
Some may choose to buy polycrystalline solar panels because they’re cheaper than monocrystalline panels and less wasteful. They’re less efficient and bigger than their more common counterparts, but you might get more bang for your buck if you have abundant space and access to sunshine.
Thin-film solar panels are lightweight and flexible, so they can better adapt to unconventional building situations. They’re also much cheaper than other types of solar panels and less wasteful because they use less silicon.
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