Electricity from the sun
Photovoltaic (PV) cells are semiconductors that convert sunlight into electricity. Typically, a silicon PV cell is a thin wafer with an ultra-thin layer of phosphorus-doped silicon applied on top of a thicker layer of boron-doped silicon. The phosphorous-doped silicon is an N-type material while the boron-doped silicon is a P-type material. The area where these two materials are in contact is the P-N junction. When sunlight strikes the surface of a PV cell, the electrical field that the P-N junction creates near the top surface of the cell provides momentum and direction to light-stimulated electrons, which results in a flow of electrical current when the cell is connected to an electrical load. Current flows in one direction, hence it is direct current (dc).
The two types of PVs manufactured are silicon cell (monocrystalline and polycrystalline) or amorphous silicon. Under open-circuit, no-load conditions a typical silicon PV cell produces about 0.5 Vdc, regardless of its size. However, the current that a PV cell produces depends on its surface area, efficiency, and the intensity of sunlight striking the cell’s surface.
In other words, the P-N junction produces its typical half-volt difference in potential, but the presence of sunlight produces the “push” that causes current to flow.