The conversion of electromagnetic radiation like sunlight into electricity through absorption by a semiconducting material is known as photovoltaic effect. Devices based on this effect, such as the photovoltaic cell serve as power sources in remote terrestrial locations, satellites and other space applications. These constitute the basic units by which solar energy is converted to usable electric power. Solar power automobiles and aircrafts have also been demonstrated. Photovoltaic cells are used extensively in photographic exposure meters and in light-operated relay systems used in automation.
In the modern photovoltaic cell light falls upon a junction called a barrier layer between two different types of semiconductors, an ‘n-type’ (negative) and ‘p-type’ (positive). This results in the generation of an electric current. The semiconductors are made of glassy selenium, or crystalline or amorphous silicon.
