Selenium Cell

A selenium cell, also referred to as selenium photocell, is a photo-electric element which generates a voltage upon illumination. They were the first photovoltaic cells. You are no longer used today, and have largely been replaced in the applications by photodiodes.

Construction

Selenium cells consist of a nickel-plated iron base plate on which a polycrystalline selenium layer. A cover having a thin layer of transparent cadmium oxide ( CdO ), is used.

Function

A barrier layer between the selenium and forming a transparent CdO layer. By light irradiation, electrons are released, which migrate through the influence of the electric field in the direction of the neutral ( space-charge- free ) area of ​​the CdO layer. The holes move in the neutral region of the selenium layer. This generates a voltage between the two areas that can be tapped between the base plate and the cover ring is formed.

Historical applications

After preparatory work in the UK by William Grylls Adams and Charles Fritts built the first other selenium cell around 1883 in New York.

The application of the selenium cell was decades in light meters in cameras, as for exposure no further energy source (battery) was needed. You are here mostly hidden behind a diffusing glass and can easily also by their greater surface differ from the photoresistors also used. Because of the insufficient resistance to aging, they are no longer used today.

• Semiconductor device
• Camera technology
• Historical electric appliance