Photocathode

A photocathode (also photocathode ) is a detector for photons, which converts utilizing the external photoelectric effect incident photons into free electrons.

Photo cathodes consist of a thin semiconductor or metal layer with a low work function, which is applied in an evacuated tube on the inside of a window ( as the transparent supporting substrate ). The layer thickness is typically about 10 nm, so that the layers are semi-transparent.

Older photocells carrying the photocathode on the inside of the back of the glass bulb; the layer thickness could be higher in these. The spectral sensitivity varies depending on the material and is in the range between near-ultraviolet and near infrared.

Photocathodes are used not only in photocells, inter alia, image converter tubes, image intensifiers, photomultipliers and image pickup tubes.

Photocathodes of vidicons ( image pickup tube ) consists of individual, mutually isolated metal islands. The image information is formed as a charge image and is read with an electron beam. Conversely, can be studied in terms of their structure and surface material composition by irradiating the photo-cathode in a vacuum to light of certain wavelengths, and thus, the work function is determined ( photoelectron spectroscopy).

Swell

• Electron tube
• Sensor