Electroluminescence

Electroluminescence (EL) is an optical and electrical event in which a material emits light in response to an electric current passed through it, or to a strong electric field.

Electroluminescence Media

Views of a liquid crystal display, both with electroluminescent backlight switched on (top) and switched off (bottom)
Spectrum of a blue/green electroluminescent light source for a clock radio (similar to the one seen in the above image). Peak wavelength is at 492 nm and the FWHM spectral bandwidth is quite wide at about 85 nm.
1966 Dodge Charger instrument panel with "Panelescent Lighting". Chrysler first introduced cars with EL panel lighting in its 1960 model year.
An electroluminescent nightlight in operation (uses 0.08 W at 230 V, and dates from 1960; lit diameter is 59 mm)
A Casio digital LCD watch with an electroluminescent backlight

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The electric energy is absorbed by electron in the ground state and is excited to the higher state of energy called the excited state.The excited state is not the stable state and the electron jumps back to the ground state and emits the photon related to the bandgap of the material.