A solar cell (or a "photovoltaic" cell) is a device that converts photons from the sun (solar light) into electricity.
In general, a solar cell that includes both solar and nonsolar sources of light (such as photons from incandescent bulbs) is termed a photovoltaic cell.
Fundamentally, the device needs to fulfill only two functions: photogeneration of charge carriers (electrons and holes) in a light-absorbing material, and separation of the charge carriers to a conductive contact that will transmit the electricity.
This conversion is called the photovoltaic effect, and the field of research related to solar cells is known as photovoltaics.
Solar cells have many applications.
Historically solar cells have been used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth orbiting satellites, consumer systems, e.g. handheld calculators or wrist watches, remote radio-telephones and water pumping applications.
Solar cells are regarded as one of the key technologies towards a sustainable energy supply.