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
. Before emission, 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 an emission of light 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.