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.
Inside a Solar Cell
We’ve seen them for years on rooftops, atop highway warning signs, and elsewhere, but how many of us know how solar panels actually work? How do the photovoltaic cells that lie at the heart of them turn sunlight (photo) into electricity (voltaic)? Below, familiarize yourself with the parts of a basic photovoltaic cell, and find out how it goes about harnessing the free energy of the sun.—Stephanie Chasteen and Rima Chaddha
Anatomy of a solar cell
Solar panels capture sunlight and convert it to electricity using photovoltaic (PV) cells like the one illustrated above. Such cells, which can power everything from calculators to cars (our example will be a house), have several components. First, and most obviously, are two layers of silicon. These make up the bulk of the cell, and, as we’ll see, the plane where they meet is where much of the key action takes place. The cell also has metal strips that conduct the flow of electrons (the electricity that the cell produces) through wires into the house, where it powers electrical appliances. Electrons also flow back out of the house and return to the cell through the cell’s metal backing, in order to make a closed loop. Finally, the cell bears an antireflective coating, which ensures that photons—the particles of sunlight needed to generate solar power—are absorbed by the silicon layers and not reflected away.
Silicon is a strong and stable building material for PV cells, but on its own it makes for a poor conductor. So manufacturers beef up or dope the cell’s two silicon layers with trace amounts of additives, typically phosphorus and boron. The top, phosphorus-doped layer contains more electrons, or negatively charged particles, than pure silicon does, while the bottom, boron-doped layer contains fewer electrons. This difference is crucial, as the next entry reveals.
The electric field
To generate electricity, we first need to establish an electric field. It’s like a magnetic field: just as the opposite poles of two magnets attract each other, so do the positive and negative charges in an electric field. This opposites attract electric field is created in the cell when its two different silicon layers are first brought together in the factory. The extra electrons in the phosphorus-doped top layer naturally move into the boron-doped bottom layer—a process that occurs in a fraction of a second and only very close to the junction (the point at which the two layers meet). Once the bottom layer has gained extra electrons, it becomes negatively charged at the junction; at the same time, the top layer has gained a positive charge there. Now the cell is ready for the sun.
As sunlight hits the cell, its photons begin knocking loose electrons in both silicon layers. These newly freed electrons dart around each layer but are useless for generating electricity unless and until they reach the electric field at the junction. (This relative inefficiency compared to that of fossil fuels is part of the reason why solar cells still only account for less than 0.1 percent of the energy used in the U.S.) The electric field pushes electrons that do reach the junction towards the top silicon layer. This force essentially slingshots the electrons out of the cell to the metal conductor strips, generating electricity.
Powering the house
Electrons flow as electricity via the metal conductor strips into a wire and thence to an inverter inside the house. This device converts the direct current coming from the PV cell into the alternating current our appliances can use. As noted earlier, electrons also flow out of the house and back to the solar panel, creating the closed loop necessary to maintain the flow of electricity. The cell keeps generating electricity, even on cloudy days, until the sun goes down at night. To see solar power in action, check out This Solar House.
We recommend you visit the interactive version. The text to the left is provided for printing purposes.
- New Ways to Catch Rays
- Ask the Expert
- This Solar House
- Inside a Solar Cell
Stephanie Chasteen is a postdoctoral fellow in physics at the Exploratorium in San Francisco. She earned a Ph.D. in physics at UC Santa Cruz, where she researched ways to generate solar energy from semiconducting plastics. Rima Chaddha is an assistant editor of NOVA online.
Early – Mid 1900s
This century included even more discoveries and advancements which furthered human understanding of materials and the photoelectric effect. Solar cell history and milestones were certainly much more impactful in this century.
The Photovoltaic effect demonstrated in a solar panel as the process by which electricity is generated from sunlight. Image courtesy of energyeducation.ca
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(1904) Wilhelm Hallwach discovers photosensitive combination of copper and cuprous oxide
(1905) Albert Einstein published a paper on the photoelectric effect
(1916) Robert Millikan provided experimental proof of photovoltaic effect
(1918) Jan Czochralski developed a method for growing single-crystal silicon
(1932) Audobert and Strora discover photoelectric effect in cadmium sulfide
(Mid-1900s) The mid 1900s introduced the solar era of solar cell history and milestones. 1954 marked the year photovoltaic technology was officially born. In the United states Daryl Chapin, Calvin Fuller and Gerald Pearson developed the Silicon PV cell at Bell Labs. This cell began with 4% efficiency which was later increased to 11%. From this point on solar cell and solar panel history exploded with discoveries and implementations. Further readings provide a much deeper look at these events.
(1964-1966) Due to an increase in viability, solar power began to be utilized and researched much more seriously. Solar arrays were even included on the first Nimbus spacecraft (1964) and NASA’s first Orbiting Observatory (1966).
Artist rendition of OAO 1 in orbit, showing its inclusion of solar panels which were included in future OAO. Image courtesy of Wikipedia
(Early 1970s) In the 1970s Dr. Elliot Berman designs a much cheaper solar cell which reduced the price per watt down from 100/watt to 20/watt.
(1976) David Carlson and Christopher Wronski fabricate first amorphous silicon photovoltaic cells
(1977) U.S. Department of Energy launches Solar Research institute
(1980) University of Delaware develops first thin-film solar cell with over 10% efficiency using copper sulfide/cadmium sulfide
(1985) University of South Wales creates silicon solar cell with over 20% efficiency
(1992) University of South Florida develops 15.9% efficient thin-film cell made of cadmium telluride
(1994) The National Renewable Energy Laboratory (NREL) develops an over 30% efficiency solar cell made from gallium indium phosphide and gallium arsenide
(1999) National Renewable Energy Labs creates a thin-film cell with 18.8% efficiency
Today solar cells and solar panels have found a market on earth. Increasing efficiency with diminishing cost makes solar power all the more appealing. Consider the efficiency and capital cost over time graphs shown below. These grapes are specifically for Crystalline Silicon, Thin-Film Cells, and Concentrator cells.
PV system efficiency from 1995 to 2020. image courtesy of Lafayette.edu
PV system capital cost from 1995 to 2020. Image courtesy of Lafayette.edu
The result of these trends resulted in solar array implementation in various locations. From NASA utilizing solar panels on virtually every craft sent to space to Home Depot selling residential solar power systems (2001). Government bodies such as NASDA began solar projects which used solar powered systems to begin transmitting power (2001).
By the 2010s had fallen by 70%, this brought solar power to finally be competitive with other forms of electricity generation.
(2011) U.S. DOE launched the SunShot Initiative which drove costs down significantly by 2017.
Price per watt of solar cells from 2011 onward, courtesy of ae-solar.com
Private companies have begun developing their own private solar cells by the 2010s which are not on the market. These cells have reported incredible efficiencies reaching as high as 44%.
While research on solar cells has not stopped, the technology has advanced enough to be widely implemented worldwide.
How Have Solar Panels Changed Over Time
Solar panel technology today
Since its inception, solar power technology has constantly progressed. Advancements in photovoltaics (PV) and concentrated solar power (CSP) have produced a more effective hybrid technology for solar panel engineering, and have helped lower the cost significantly.
In 2016, MIT researchers produced ultra-slim, flexible solar cells that are only 1.3 microns thick. These lightweight cells weigh the same as soap bubbles, allowing future opportunities for use in certain technologies like cell phones. According to MIT, “conventional silicon-based solar modules produce about 6.8 watts per pound, but these new devices can generate more than 2,720 watts per pound, https://energy.gov/eere/videos/energy-101-solar-pv 400 times as much.” While this advancement is still in the early phases, it could help widen the use of solar technology.
Continued scientific advancements have made vast improvements in solar panel technology, including increasing the capacity to harness more solar energy per unit of surface area. This is a vital factor in panel technology because the more energy a solar panel can absorb, the more efficient the panel becomes at harnessing solar energy. Today, solar panels can deliver at up to 22% efficiency. There have also been ongoing efforts to make solar energy even more affordable and efficient with an emerging technology called the “perovskite” solar cell. This crystalline material could ultimately replace silicon in solar panels and reduce costs using simpler production methods.
The future of solar panels looks promising, with technological advancements and cost-reduction efforts continuing to drive availability. Solar panel technology is now being used in small-scale applications like powering homes and businesses, as well as large-scale ones such as generating electricity for entire cities. Today, solar energy is a viable option for individuals looking to reduce their carbon footprint and save money on energy costs. With continued research and development, solar panel technology is likely to become even more cost-effective in the near future. This will make it an increasingly attractive option for many looking to reduce their environmental impact and power their lives with clean energy.
Explore Solar Power Through Community Solar
Today, most of the electricity generated in the U.S. comes from fossil fuels, like natural gas, coal, and petroleum. Renewable power accounts for just fewer than 15% of U.S. electricity generation, with solar accounting for.9%. As technologies evolve and are optimized, and solar power becomes more accessible and convenient through programs like community solar, there is hope that our production will shift and the solar energy share will grow. The infinite power of the sun is there, waiting for us to harness it.
At Clearway Community Solar, we’re creating pathways for individuals, businesses, and communities to directly access solar power. Our mission is to make solar more accessible by allowing people to reap the benefits of clean energy without having to install panels on their roofs or own any equipment. By joining a community solar farm in your area, you can start saving money on your electricity bills while also doing your part to reduce our global dependence on fossil fuels.
In a community solar farm. individuals can receive credits for the energy produced by their share of solar panels. This helps make it easier for people to switch to renewable energy without purchasing or maintaining their own equipment. We’re committed to making the switch to solar power as easy as possible so that everyone can benefit from its benefits. To learn more about our solar farms, contact us today !
What is the latest technology in solar panels?
The latest technology in solar panels is the perovskite solar cell. This crystalline material could replace traditional silicon-based solar cells and reduce costs using simpler production methods.
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Is solar panel technology improving?
Yes, solar panel technology is improving. Ongoing research and development efforts have improved efficiency and lowered costs for solar panel technology. As new technologies are developed and cost-reduction efforts continue, solar energy will become a more viable option for individuals looking to reduce their carbon footprint and save money on electricity bills.
Will solar panels ever reach 50% efficiency?
While 50% efficiency is theoretically possible with solar panel technology, it would require significant technological advancements. Currently, the highest efficiency of commercially available solar panels is around 22%. However, this number may continue to increase with ongoing research and development.
What is community solar?
Community solar is a model of renewable energy generation that allows individuals to benefit from the power of solar energy without having to install their own system. It works by establishing a shared facility that houses solar panels and then distributing the electricity generated from those panels among participants. This is an attractive option for people who cannot or do not want to install their own systems.
How does community solar impact the development of solar panels?
Community solar projects make it possible for more people to access the benefits of solar energy, which can positively impact the development of solar panels. By increasing awareness of solar power’s potential and availability, solar community projects can help spur continued research and development into new technologies that will improve efficiency and reduce costs. This could drive the development of solar panels and make them more accessible to a wider range of people.