Solar electricity generation (PV)
Here are two explanations of how solar cells work. Note that the first one is complex, and the second is really complex!
Here are a couple of ways to make your own solar cells. Neither of them is very practical, or produces much charge. The first is reasonably simple, the second is extremely complex and just FYI.
Here is a video that expands on and refines the first of these options...
Here is another video of someone making a solar cell. This time, it's out of old CDs. This looks great and so easy!...but hold on a sec - does is really work? Why not give it a go using a single CD and testing it out with a multimeter.