Beneath a glass panel and an anti-reflective coat, rest two thin layers of silicon. The top layer boasts a surplus of electrons, while the bottom layer bears a deficit. When particles of light pass through the top layer, they knock surplus electrons free. The newly liberated electrons move through the bottom layer of silicon and flow through the metal plates lining the cell. From there, they travel by wire to their final destination — be it a cell phone, laptop or electric car.