Solar Cell is a kind of device that responses light and then transform light into electric power. There many materials to cause photovoltatic effect, such as monocrystalline silicon, polycrystalline silicon, amorphtus silicon, GaAS,CIS etc. Their principles of generating electricity are nearly same. Now we will discribe the procedure of transforming light into electricity. After mixing phosphor, P-crystalline silicon can get N-crystalline silicon, and come into being P-N tie, when the straight light sheds on the surface of solar cell, a part of light is absorbed by the silicon, the energy of photons passes to atoms of silicon which makes the electron moves, and the free electron shapes a potential difference on the sides of P-N tie. When the outside circuit get through , by the effect of voltage, the circuit generates a certain of output power through the outer curcuit. The essence of the procedure is photrons energy tranforms into electric power.