Electroluminescence

Introduction :

The first electroluminescence effect was observed when a phosphor powder such as ZnS, placed in a plastic or glass capsule, was subjected to an electric field. The light was produced by phosphor had low efficiency.

Definitions :

When the luminescence occurs due o the introduction of electric field or current, it is known as electroluminescence.


                             OR


When electric energy is used to generate photon emission, the mechanism is known as electroluminescence.

Methods:

Injection electroluminescence is most important method of excitation. LEDs which is known as Light Emitting Diodes are P-N junction that under forward biased condition or reversed-biased junctions can emit external spontaneous radiation. In LEDs an electric current cause the injection of minority carriers into regions of crystal where they recombine with majority carriers. This results in the emission of recombination radiation. This effect is known as injection electroluminescence.

Electroluminescence can also result from tunneling into forward-biased or reverse-biased junction as well as by avalanche excitation.