Definition of Electroluminescence
Electroluminescence (EL) is an optical and electrical phenomenon where a material emits light in response to the passage of an electric current or to a strong electric field. Unlike incandescence, which produces light through heat, EL is a 'cold light' process, meaning it generates light without significant heat production.
Mechanism of Light Emission
The emission of light in electroluminescence occurs when electrons are excited by an electric field and then release their energy as photons. This excitation can happen in a few ways: either by direct impact ionization (where electrons directly hit and excite atoms), or by injection and recombination (where electrons and holes are injected into a semiconductor, and their recombination releases energy as light). The specific mechanism depends on the type of electroluminescent material.
Common Examples and Applications
A common practical example of electroluminescence is found in Light Emitting Diodes (LEDs), though they primarily operate via injection electroluminescence. Other applications include electroluminescent panels used for backlighting in watches, instrument displays, and advertising signs. Electroluminescent wires (EL wire) also utilize this principle, emitting a uniform glow along their length for decorative and safety purposes.
Advantages and Limitations
The primary advantages of electroluminescent materials include their low power consumption, thin profile, uniform light emission, and durability. They produce very little heat, which contributes to their energy efficiency. However, a limitation is often their brightness, which can be lower than other light sources, and their lifespan can be affected by humidity and temperature, leading to gradual degradation over time.