What is Electroluminescence?

Electroluminescence is an optical and electrical phenomenon. It is a light emission response of a material when a electrical current is passed through it. This is different from light emission resulting from heat (incandescence) or from the action of chemicals (chemo luminescence). Electroluminescence is the conversion of electricity directly into light.

Luminescence, in contrast, is the name given to "all forms of visible radiant energy due to causes other than temperature." When an electric charge is passed through the material (usually a semiconductor) the excited electrons release their energy as photons - light. This process is quite similar to that of capacitors except for the phosphor layer (the powder found in tubular strip lights) which emits the light.

electroluminescent (EL) device is similar to a laser in that photons are produced by the return of an excited substance to its ground state, but unlike lasers EL devices require much less energy to operate and do not produce coherent light.

Electroluminescent displays have at least six layers. The first layer is a base plate (usually a rigid insulator like glass), the second is a conductor, the third is an insulator, the fourth is a layer of phosphors, and the fifth is an insulator, and the sixth is another conductor. The insulator layers are necessary to prevent arcing between the two conductive layers.

Electroluminescent displays can be thought of as a "lossy capacitor" in that it becomes electrically charged and then loses its energy in the form of light. An alternating current (AC) is generally used to drive an ELD because the light generated by the current decays when a constant voltage is applied

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