How solar cells work?

 How can you catch sunlight and do something useful with it? Plants do that naturally, but it took us a long time to invent solar cells. Here's how they work. There are two layers of a semiconductor, such as silicon, joined together. The upper layer (blue) is chemically treated ("doped") so it has extra electrons - it's called n-type; the lower layer is also doped, but made to... have fewer electrons - p-type, we call it. When sunlight (1) shines on the cell, photons (energetic light particles) enter the n-type layer (2). The photons give up their energy to electrons in the p-type layer (3), which jump over the barrier into the n-type layer (4). Connect the cell to a circuit and the electrons flow out around it (5). We just turned sunlight into electricity!