Photoleiter

A photoleiter, also known as a photoconductor, is a semiconductor material that exhibits a significant change in electrical conductivity when exposed to light. This phenomenon is the basis for many optoelectronic devices, including photocells, photodetectors, and photocopiers. Photoleiters are typically made from materials such as cadmium sulfide (CdS), cadmium selenide (CdSe), lead sulfide (PbS), or organic polymers, which have a bandgap that allows them to absorb photons and generate electron-hole pairs.

The operation of a photoleiter relies on the photoelectric effect, where incident photons with sufficient energy (greater than the material’s bandgap) excite electrons from the valence band to the conduction band, increasing the number of charge carriers and thus conductivity. In the absence of light, the material behaves as an insulator due to the absence of free charge carriers. When illuminated, the increased conductivity allows the material to conduct electricity, enabling its use in light-sensitive applications.

Photoleiters are commonly used in light meters, exposure meters in photography, and as sensors in industrial automation. They can also be integrated into photomultiplier tubes and other high-sensitivity detection systems. The response time of a photoleiter depends on the material properties and the recombination rate of electron-hole pairs, with some materials exhibiting fast responses suitable for high-frequency applications.

In addition to inorganic photoleiters, organic photoleiters, such as certain polymers and small molecules, have gained attention due to their flexibility, low-cost processing, and potential for large-area applications. These materials are particularly useful in flexible electronics and organic photovoltaics. The efficiency and stability of photoleiters can vary widely depending on the material composition, doping, and environmental conditions, making material selection critical for specific applications.