Electroluminescence

Electroluminescence is an optical phenomenon and electrical phenomenon where a material such as a natural blue diamond emits light when an electric current is passed through it.

Electroluminescence (EL) is mainly observed in semiconductors. It refers to the luminescence produced by some materials when exposed to an electric field, as opposed to heat (incandescence) or chemicals (chemoluminescence). The electric field excites electrons in the material which then emit the excess energy as photons (light).

LEDs are the most well known example of electroluminescence.