How in the world do solar panels work?
It sounds like magic: Capturing energy from the sun and converting it into electricity to run your toaster. It's science, not magic, though. Solar panels use a curious bit of science called the photovoltaic effect to convert one form of energy into another. Here's how solar panels harvest light, converting it into electricity.
The sun is an intense powerhouse, outputting in the region of 10 decillion (that's a 1 followed by 34 zeroes) joules of energy per year. That's a lot. The whole planet is bathed in this wash of energy, and it is one of the things that makes this such a pleasant place to live. It drives the weather, heating the atmosphere and making life possible. So, wouldn't it be useful to be able to convert some of this energy into a form that we could use?
That's what plants do through photosynthesis, using light to combine carbon from the atmosphere into sugars that they metabolize to grow. And the solar panels that you see on an increasing number of roofs do something similar, converting light into electricity. They can do this because of something called the photovoltaic effect, which converts solar energy into electrical energy.
It works like this: sometimes, when light hits an atom, it is absorbed by one of the electrons around the atom, boosting the energy of the electron. On some materials (such as some metals and silicon), this extra energy is enough to kick the electron loose of the atom, letting it move within the crystal structure of the material. If you create two crystal layers, you can exploit this.
One layer, called an N-type material, is contaminated with a chemical (scientists call this doping) that means there are lots of electrons in it, so it has electrons to spare. The other layer is contaminated with another material that makes it want to soak up more electrons, called a P-type material. These electrons can't easily jump over the junction of these two materials (called an NP junction), so there's a voltage difference between the two layers. If you then connect a circuit to each side of this panel, that voltage can be used to power an appliance, or to charge a battery.
Each solar cell generates only a small voltage, typically about 0.5V. The amount of current created depends on the size of the cell. If you connect multiple cells together, this voltage can be increased. So, if you cover your roof with solar cells wired together, you can harvest enough electricity to power most of the house.