Luminescence is a physical phenomenon in which electrons with a higher energy level fall to a lower one, causing emissions, for example as electromagnetic radiation or in the form of light.
Prior to emission, the electrons are transferred from a lower level to a higher level by adding energy. Since the electrons cannot stay at this level for long, they fall back and trigger the emission.
Luminescence can be a light emission in the visible or ultraviolet wavelength range, and it can also appear as X-rays, radioactive or electromagnetic radiation. The effect of electroluminescence is caused by electric fields and is used in light-emitting diodes and EL films. OLEDs use the effect of organic electroluminescence.