photoconducteurs

Photoconducteurs are semiconductor materials that exhibit photoconductivity. Photoconductivity is the phenomenon where a material increases its electrical conductivity when exposed to electromagnetic radiation. This radiation can be in the form of visible light, ultraviolet light, or infrared light. The underlying principle involves the absorption of photons by the semiconductor, which excites electrons from the valence band to the conduction band. This process generates electron-hole pairs, which are mobile charge carriers. The increased number of charge carriers leads to a decrease in electrical resistance and thus an increase in conductivity.

The sensitivity of a photoconductor to light is often described by its spectral response, which indicates the range of wavelengths to which it is most sensitive. The speed of response, or how quickly the conductivity changes upon illumination and returns to its dark conductivity when the light is removed, is also an important characteristic. Common materials used as photoconductors include cadmium sulfide (CdS), cadmium selenide (CdSe), selenium, and amorphous silicon. These materials are employed in a variety of applications due to their light-sensitive properties.

Applications of photoconductors are diverse and include light sensors, photocopiers, solar cells, and charge-coupled devices (CCDs) used in digital cameras. In photocopiers, a photoconductive drum is charged, and then illuminated by a light image. The illuminated areas lose their charge, creating an electrostatic image that attracts toner particles. In light meters and sensors, the change in conductivity is measured to determine the intensity of light. The continuous development of new photoconductive materials aims to improve sensitivity, speed, and spectral range for even broader applications.