Electroluminescence

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Electroluminescence (EL) is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field. This is distinct from black body light emission resulting from heat (incandescence), from a chemical reaction (chemiluminescence), sound (sonoluminescence), or other mechanical action (mechanoluminescence).

Contents

Mechanism

Electroluminescence is the result of radiative recombination of electrons and holes in a material, usually a semiconductor. The excited electrons release their energy as photons - light. Prior to recombination, electrons and holes may be separated either by doping the material to form a p-n junction (in semiconductor electroluminescent devices such as LEDs), or through excitation by impact of high-energy electrons accelerated by a strong electric field (as with the phosphors in electroluminescent displays).

Examples of electroluminescent materials

Electroluminescent devices are fabricated using thin films of either organic or of inorganic materials. The thin film layers contain a bulk semiconductor (or host material for organic electroluminescence ) and a dopant which defines the visible color emitted. The semiconductor needs to have wide enough bandwidth to allow exit of the light.

The most typical inorganic thin-film EL (TFEL), for example, is ZnS:Mn with its yellow-orange emission. Examples of the range of EL material include:

Practical implementations

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