fotoconductor

Fotoconductor, or photoconductor, is a material whose electrical conductivity increases when it is illuminated by light. Unlike devices that directly convert light into electrical power, a photoconductor responds to light by changing its conductivity, enabling light sensing and signal processing.

The photoconductive effect occurs when photons with sufficient energy generate charge carriers, such as electrons and holes, within the material. This increased carrier concentration raises the material’s conductivity. The response depends on the band structure, impurities, and trap states; carrier generation, recombination, and trapping influence both the magnitude of the effect and the response time.

Common photoconductive materials include inorganic semiconductors such as cadmium sulfide (CdS) and cadmium selenide (CdSe), as well as amorphous selenium used in xerographic processes. Organic photoconductors and polymer-based systems have also been developed, offering flexible and image-friendly options for sensing and imaging applications.

Applications of photoconductors span light meters and exposure sensors in photography, photodetectors in consumer electronics, and xerographic copy processes. They are also used in certain infrared detectors based on narrow-gap materials. The technology supports a range of sensing tasks where a controllable change in conductivity in response to light is advantageous.

Historically, photoconductivity was studied with early materials like selenium, leading to devices such as photoresistors and photoconductive charging drums used in copying technologies. See also photoconductivity, photoresistor, and xerography.