fotocellule

Fotocellule, typically referred to in English as photocells, are electronic devices that respond to light. They can either generate an electrical signal from light (photovoltaic effect) or change their electrical resistance as illumination varies (photoconductive or light-dependent resistor behavior).

Major families include solar cells, which convert light directly into electricity; light-dependent resistors (LDRs or CdS cells), whose resistance falls as light intensity rises; and photodiodes or phototransistors used for fast, linear light sensing. Each type uses semiconductor materials and a different operating principle to detect light across a portion of the spectrum.

Applications of photocells are diverse. They enable automatic lighting and daylight harvesting, camera exposure metering, safety and security sensors, optical switches, and measurement instruments. Solar cells in photovoltaic arrays also form the energy supply for remote systems and consumer electronics.

Historically, the study of light-induced electrical effects began with the photoelectric effect in the 19th and early 20th centuries, leading to the development of detectors and semiconductor devices. Modern photocells rely on silicon and other semiconductors and date from mid-20th century advances in optoelectronics.

See also: Photodetector, Solar cell, Light-dependent resistor, Photoelectric cell.