Electroluminescence panels (EL panels) emit light when electric current passes through them. The panel is made of electroluminescent materials with semiconductor properties, having a wide bandwidth to allow exit of the light. The common materials used include powdered zinc sulphide doped with copper, thin-film zinc sulphide doped with manganese, or powder phosphor. The EL material is enclosed between two electrodes, with at least one electrode transparent, facilitating the escape of light. When current is applied to the panel, the electrons of the EL material undergo radiative recombination with the holes in the material. The excited electrons release energy as photons or light. EL panels have many applications, in LED lighting systems, in nightlights and backlights for instrument panel displays, in computer controlled thermostats, in wristwatches, and more. These panels are highly reliable and have a very long life. They consumes very little power, while still lighting up the display over a wide area. The brightness per unit area depends on the applied voltage and frequency, with increased voltage and frequency increasing the brightness. EL panels that receive current from batteries require an EL inverter, to convert the DC current to AC current. EL panels come in different colours, such as green, blue or white, and in different dimensions.