And no don’t say “cells generate electricity” Yes I know that, but what chemical or whatever process makes it that sunlight is converted to electricity?
I have been wondering this all my life an no matter how much research I do I can’t seem to find the answer, every place just says that some cells inside the panels is what generates electricity, but not how those cells do it
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The light kicks out electrons from their stable position. Those electrons can then circulate in a circuit to go back to a hole made by another electron kicked out from its stable position.
In an LED an electron falls into a hole, and instead of screaming it shines. The depth of the hole determines the colour of the emitted light.
A solar panel works the other way around: incoming light moves the electron out of the hole, from where it can participate in being electrical current.
Wow, I never thought I’d thank my LEDs for powering my home. They’re finally pulling their weight!
Light is made out of photons, which are like tiny little energy packets. Atoms are made of protons, neutrons, and electrons, with the electrons on the outside and the protons and neutrons packed into a tiny spot in the center, called the nucleus. When photons hit electrons, the electrons absorb them and their energy increases. The amount of energy the electron has determines how far away from the nucleus it is. If it gains enough energy, it can jump all the way off and be freed from the atom.
Solar cells arrange atoms in such a way that when light hits them, the electrons absorbing the energy from the photons move away from their nuclei and towards wires, which push the electrons inside the wires away. Those electrons push their neighbors away, and so on, all the way through the wire. Electrons moving through wires is what we call “electricity.”
That’s the version for 5-year olds. If you want it explained like you are in college, the wikipedia article is pretty good: https://en.wikipedia.org/wiki/Theory_of_solar_cells
It all comes down to light knocking electrons out of place. This is called the photoelectric effect. Light comes in, and if it has enough energy, it can knock the electron off of an atom and we funnel that away to make electricity.
We can manage that funneling with very carefully manufactured silicon. Silicon has 4 valance (outer) electrons. That means in a silicon crystal, each atom bonds to 4 neighbors. You can think of it like a grid, but in reality, it’s a tetrahedron shape. By adding atoms with 5 valance electrons, they can replace some of those silicon atoms in the structure. With those 5 valance electrons, it still bonds to its 4 neighbors, but it has an extra electron that is free to move around. This is called N-doped silicon (N because of the extra negative charge). We do the same with an atom with 3 valance electrons to make P-doped silicon. Basically, it forms the same bonds with its neighbors, except now there’s a hole where an electron could be in one of those bonds. Neighboring electrons can move to fill that hole, but it leaves a hole where it came from. We treat this like a free floating positive charge (hence P-doped silicon).
When we put the P and N doped silicon next to each other, some of those extra electrons and holes will find each other, and the electrons fill the holes. This creates a region with no free electrons or holes called the depletion zone. Since the N doped silicon has lost an electron and the P doped silicon has gained an electron, this gives the N doped side a positive charge, and the P doped side a negative charge, and a small electric field across the depletion zone. This is exactly how a diode works, the electric field allows electrons to flow one way and not the other.
When light with enough energy comes in, it knocks an electron off with enough energy to cross the depletion zone (the wrong way), which gives it enough potential energy to do work. We send the electron on it way down a wire where it can be used as electricity.
Imagine it like a slide. The light lets the electrons climb a ladder and lets it slide down (move through the wire) until they eventually make it all the way through the circuit and back to the ladder.
Fun fact: solar panels are the only power generation method we use that produces DC current rather than AC. We need to convert it to AC before it can enter the grid. (Batteries also produce DC power, but they aren’t on the grid)
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