Electroluminescence can be exploited in light sources. Such sources typically emit from a large area, which makes them suitable for backlights of LCD displays. The excitation of the phosphor is usually achieved by application of high-intensity electric field, usually with suitable frequency. Current electroluminescent light sources tend to degrade with use, resulting in their relatively short operation lifetimes.
ZnS:Cu was the first formulation successfully displaying electroluminescence, tested at 1936 by Georges Destriau in Madame Marie Curie laboratories in Paris.
Powder or AC electroluminescence is found in a variety of backlight and night light applications.  Several groups offer branded EL offerings (e.g. IndiGlo used in some Timex watches) or "Lighttape", another trade name of an electroluminescent material, used in electroluminescent light strips.  The Apollo space program is often credited with being the first significant use of EL for backlights and lighting.