A PV cell consists of two thin layers of semi-conducting silicon. Each layer is “doped,” or infused with a small amount of another material that prevents all the electrons from being locked in the pure silicon lattice structure.

One layer is doped (usually with phosphorus) so that it has slightly too many electrons, and the other layer is doped (usually with boron) so that it has slightly too few electrons. This difference produces a small electric field between the two layers, which gives the electrons a direction to flow when they get knocked out of place by a photon (packet of light energy).

Solar cells are usually small and only produce a couple of watts of power. To produce usable energy, many cells are strung together to make a module. Multiple modules are connected into an array, which gets connected to a load (like a light bulb). Through the wiring the electrons have a chance to flow through the whole loop back to the layer that lost its electrons in the first place.

The electric current, as this flow is called, has done some work (making light and heat in the light bulb).