Solar cells convert sunlight directly into electricity. Solar cells are often used to power calculators and watches. They are made of semiconducting materials similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect. If light energy strikes the surface of some semiconductor materials, they emit electrons. These freed electrons can then be made to flow in a circuit.
The principle is applied in some ignition systems, and vehicle speed sensors. In addition, it is the principle of the solar cell. Solar cells are becoming more prevalent in the automobile industry.The term "photovoltaic" comes from the Greek photos meaning light and the name of the Italian physicist Volta, after whom the volt (and consequently voltage) are named. It means literally of light and electricity.