Fotokonduktansen

Fotokonduktansen is a phenomenon where the electrical conductivity of a material changes when it is exposed to light. This change is due to the generation of charge carriers within the material when photons are absorbed. When light strikes a semiconductor, its photons can excite electrons from the valence band to the conduction band, creating both free electrons and holes. These mobile charge carriers increase the material's electrical conductivity. The extent of this increase depends on factors such as the intensity and wavelength of the light, as well as the intrinsic properties of the material, like its band gap.

Materials that exhibit strong fotokonduktansen are known as photoconductors. Common examples include cadmium sulfide (CdS), cadmium selenide (CdSe), and amorphous silicon. The spectral response of a photoconductor, meaning the range of light wavelengths to which it is sensitive, is determined by its band gap. Materials with smaller band gaps absorb lower-energy photons (longer wavelengths), while those with larger band gaps require higher-energy photons (shorter wavelengths).

Fotokonduktansen is a fundamental principle behind various optoelectronic devices. Photoconductive cells, for example, use this effect to detect light. Their resistance decreases in the presence of light, allowing them to control electrical circuits. This sensitivity to light makes them useful in applications such as automatic lighting controls, light meters, and optical switches. The speed at which a photoconductor responds to changes in light intensity is also an important characteristic, influencing its suitability for high-speed applications.