Most understand the broad sense of how solar panels work. You put them in the sun, and they take the light and turn it into usable energy. However, when it comes to understanding the specifics of it, you may be surprised to find out how it works.
There is a lot of complicated science behind how the system works, but it is relatively simple. To learn more about how photovoltaic cells work and the different kinds of photovoltaic cells available on the market, we’ve summarized them below.
What Are Photovoltaic Cells?
Also known as solar cells, photovoltaic cells are the parts of the solar panel that absorb the light from the sun and help turn it into energy. They are the main part of many different solar panels.
The name comes from the fact that photovoltaic cells create electricity via the photovoltaic effect. There are different kinds of photovoltaic cells, but they all work in similar ways.
These panels were first developed in 1960, but the effect was discovered back in 1839. They were first used with things like satellites and became something that we saw on earth on rooftops in the 1980s.
How Do They Work?
The photovoltaic effect works by having layers of different materials stacked on top of each other. The most talked about, and most important layer in the whole system is the photovoltaic semiconductor layer.
Despite being called one layer, it is actually two, the p and n-type layers. They are what convert the energy from the sun into usable electricity.
In simple terms, these layers work by separating the electrons from the atomic nuclei. When the silicon semiconductor layer is then hit by the photons, they let go of their electrons.
There are also electron holes, which are seen as the opposite of an electron. They have positive charges that are equal in magnitude to the negative charge of an electron. Technically, these holes aren’t physical particles but are actually vacant spaces where electrons should be but they are not.
The electrons and the holes, once the photons hit the silicon layer, are then left wandering while they are trying to fill the vacant space.
This isn’t enough to create electricity though. Electrons can’t just wander around randomly. Instead, they need to be able to flow in the same direction. This is where other layers come in.
One side of the layer has phosphorus, while the other side has boron.
This is important because phosphorus has one more electron than silicon while boron has one less. These are the p and n layers mentioned above.
This pulls the electrons into one direction and then creates an electron field known as a p-n junction. Electrons will move to the more positive p-side and the electron hole is moved to the n-side.
This causes the positive flow to go in one direction and the negative flow to move in the other. This movement is what creates the electron field and generates usable electricity.
There is also a layer at the top that is anti-reflective to minimize the loss of photons that often occurs due to reflection. Unfortunately, based on the information and technology we have right now, solar panels and photovoltaic cells aren’t very efficient, and can’t generate a lot of electricity based on the amount of sunlight they can take. At most, solar panels are about 22% efficient.
They also aren’t able to take a wide range of light. Most are only able to react to UV light on the spectrum. While this is one of the most abundant light ranges on the planet, it isn’t the only source of light.
If solar panels could also use light waves like infrared, they would be much more effective and useful even on cloudy days.
Combined, it forms a material that can absorb more sunlight and convert it into electricity more efficiently than traditional silicon-based solar cells. The efficiency of CIGS cells can reach up to 20%, which is one of the highest among all the other semiconductors used in solar cells.
Furthermore, CIGS cells are lightweight, flexible, and easily integrated into building materials, making them ideal for building-integrated photovoltaics (BIPV) projects. They can also convert a broader range of light into electricity, producing more power in low-light conditions.
CIGS cells have the potential to be built at a lower cost than other high-efficiency solar cells, making them an attractive option for large-scale solar power generation. Using these new semiconductors can improve the efficiency and performance of solar cells, making them a more viable source of renewable energy.
What Are the Different Kinds of Photovoltaic Cells?
There are a couple of different kinds of photovoltaic cells that you will commonly see. You have the silicon ones, the thin-film ones, and the III-V panels.
Silicon
There are two kinds of silicon solar panels; monocrystalline and polycrystalline. These are similar panels but have one major difference that makes them stand out. Their difference comes as a hint in their name.
Monocrystalline solar cells are made from a single piece of silicon. This often means there is a lot of waste, but also that they are more efficient. Unfortunately, due to the difficulty and waste that comes from making these cells, they are also more expensive.
Polycrystalline solar panels are made from multiple different pieces of silicon compressed together and tend to be a little less efficient, but they are also cheaper.
There are also now PERC cells. PERC cells are similar to monocrystalline cells but are modified to be more efficient. They have an extra layer on the back that is reflective, which sends the unused particles back through the system. This allows them to absorb more light than traditional panels would.
Because they have the extra layer, they are a little more costly, but not too much as they can be pretty easily modified from the original options.
Thin-Film
Thin-film solar panels are a little less efficient than any of the silicon ones but are still pretty feasible. There are two kinds of thin-film, which are cadmium telluride and copper indium gallium diselenide.
These work by making solar panels that are thin and somewhat flexible. Though they aren’t as efficient, they are cheap and work in places where traditional solar panels wouldn’t, such as on the top of tall vehicles, or very angled roofs. These are also able to be mass-produced with very minimal materials required.
III-V
III-V semiconductor solar cells are made from alloys that are part of groups III and IV of the periodic table. Some examples are boron, aluminum, nitrogen, phosphorus, and arsenic.
These have multiple benefits, such as having a higher absorption coefficient and it doesn’t depend on temperature as much. Gallium arsenide is the most common III-V solar cell.
The biggest problem, and why they aren’t more common despite their numerous benefits, is the cost. They are hard to make, and the process to combine all of the materials is costly as well, so the price doesn’t seem like it will come down anytime soon, unlike silicon.
Citations
- How Does a Photovoltaic Cell Work ? (n.d.). https://www.planete-energies.com/en/medias/close/how-does-photovoltaic-cell-work
- Photovoltaic cell – Energy Education. (n.d.). https://energyeducation.ca/encyclopedia/Photovoltaic_cell
- Solar Photovoltaic Cell Basics. (n.d.). Energy.gov. https://www.energy.gov/eere/solar/solar-photovoltaic-cell-basics
- Electron hole – Energy Education. (n.d.). https://energyeducation.ca/encyclopedia/Electron_hole
