The concept of solar power is astounding; the bright blue panels on your roof capture the sun, and it magically becomes electricity. Makes perfect sense, but you may ask yourself: how do those panels do what they do? It isn’t just spontaneous generation of electricity. It’s a delicate science over a century in the making.
The first step in understanding how a solar panel works is knowing the anatomy of a solar cell. A solar cell is the base unit of any panel. Many of them comprise an entire solar panel. There are a small handful of cells in development that deviate from the typical design, but these are few. There’s two layers of silicon placed in a stack, both with subtle differences, as well as rows of positive metal electrodes on top that help the silicon move the electricity generated to where it needs to be. Silicon isn’t very conductive, hence only being a semiconductor. There’s also aluminum lining under the silicon as a negative electrode, helping the power move further along. All of this is covered in an anti-reflective coating, as silicon is incredibly shiny, which can deflect photons from the sun. That’d defeat the whole purpose of the panel!
About the slight differences in the silicon layers, there are impurities put intentionally in both layers to help conductivity, as well as achieve an effect known as the positive-negative junction. This is where the magic of the solar panel happens. The upper layer, being the negative silicon layer, is compromised of silicon and phosphorus, while the lower layer is impure with boron. The obvious question is, why do these specific impurities get put into the silicon?
The answer lies in the atomic structure of each element. Silicon atoms will do whatever it needs to fill its outer shell compromised of four out of eight electrons, and usually, that means it shares some with its neighboring atoms. Typically, it’d share with four other silicon atoms, but this is where the impurities come into play.
In the upper negative layer, the phosphorus creates an abundance of electrons. Since it has five electrons in its outer shell, there’s an extra electron that is typically called a “free” electron. In the lower positive half, there’s boron, which has three electrons in its outer shell. This creates extra openings in the shells,and that’s where the negative layer’s electrons want to go.
Normally, in pure silicon, it’d be hard for these electrons to even become free from shells to do work in the first place. But thanks to how phosphorus has a free electron that’s not being held by a neighbor, electrons in silicon that’s been doped with phosphorus are easily disrupted and made loose by even just a photon from a ray of sunlight.
If those electrons all went and filled the openings in the shells, though, that’d make the whole thing useless. But as the electrons all rush to get their spot, something interesting happens. The electrons condense right at the spot between the positive and negative layers. This creates a field that makes it INCREDIBLY hard for any electron to pass over into the positive side to fill a spot. Think of it like trying to walk up a steep hill. The field created is like intense gravity. It’s easy to slip back into the negative side, but not to go into the positive one.
When the electron is bumped from its home into the negative side, it’s trying its hardest to get back. As an electron is wandering around the silicon field, it’s doing work while trying to manage its way over to the positive side. This work that’s performed is energy – direct current, anyway. This power is transformed into usable energy for your home. Underneath the layer of glass and metal is a whole lot of action happening when the sun shines down on it. Next time you see a solar panel, you can rest assured that you know exactly how it works.