photocell A device that produces an electrical signal when electromagnetic radiation falls on it. It can be a photoelectric cell where electromagnetic radiation produces photoelectrons. Electromagnetic radiation in the infrared region produces large increase in the charge carrier density in the semiconductor. A sample of semiconductor can be used in a photocell. Current through such photocell will sharply increase whenever electromagnetic waves are incident on it. Photodiodes are also used in photocells. (see also photovoltaic effect)