photodiode

photodiode

A light sensor (photodetector) that allows current to flow in one direction from one side to the other when it absorbs photons (light). The more light, the more the current. Used to detect light pulses in optical fibers and other light-sensitive applications, it works the opposite of a light emitting diode (see LED). The photodiode detects light and creates a conductive path that allows electricity to flow. The LED receives electricity and emits light.

Solar Cells Are Photodiodes
Solar cells are photodiodes that are chemically treated (doped) differently than the photodiode used as a switch or relay. When solar cells are struck by light, their silicon material is excited to a state where a small electrical current is generated. Huge arrays of solar cell photodiodes are required to power a house. See photocell and phototransistor.