Photodiode

A photodiode is a semiconductor diode that is sensitive to photon radiation such as visible light, infrared, ultraviolet, X-rays, and gamma rays, producing an electrical current when it absorbs photons, which makes it useful for light detection, measurement, and power generation in devices such as solar cells. When a photon with enough energy strikes the diode it creates an electron hole pair, and the built in electric field at the junction sweeps these charge carriers apart, sending holes toward the anode and electrons toward the cathode to produce a measurable photocurrent. The closely related phototransistor, built on similar semiconductor light sensing principles, was invented by John N. Shive at Bell Labs in 1948. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/