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


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 are separated either as a result of doping of 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 can be fabricated using thin films of either organic (see Organic Electro-Luminescence) or inorganic materials. The thin film layers contain a bulk semiconductor (or host material for organic EL) 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:

* Powder zinc sulfide doped with Copper or Silver
* Thin film zinc sulfide doped with Manganese
* Natural blue diamond (diamond with boron as a dopant).
* III-V semiconductors - such as InP,GaAs,and GaN.
* Inorganic semiconductors - such as [Ru(bpy)3]2+(PF6-)2, where bpy is 2,2'-bipyridine

see some simple examples

How do Electroluminescent sheets and film work!

A very thin layer of light emitting phosphor is placed between two thin electrodes. One is opaque and the other is translucent to allow light to escape. When AC current (400 - 1600 Hz) is applied, the phosphor will then rapidly charge and discharge, resulting in the emission of light. The brightness and color of the light depends on the chemical composition and dye pigments of the phosphor


How is EL lighting different from conventional Neon lighting!

Unlike neon signs, that use about 15,000 volts, the EL lights use a standard 12Volt AC adapter (can also be powered with a car battery, 9V and 3V alkaline battery cells).

Here is how it works: The AC adapter plugs into a standard 120Volt/60Hz outlet, the AC current is transformed to 12V DC current and goes into the inverter driver, in which the DC current is "inverted" back into AC at 120V (400 - 1600Hz). The voltage and frequency of the inverter will depend on the size of the EL lamp.

Laminating the EL lamps is important since it locks out humidity and makes them safe to handle while lit.