Electroluminescence (EL) refers to the phenomenon that luminescent material is excited by current under the action of electric field to glow. It is a luminescence process that converts electric energy directly into light energy. There are many kinds of solid materials that can produce electroluminescence, mainly divided into inorganic compound semiconductor materials and organic compound semiconductor materials. The development rate of inorganic compound semiconductor materials is higher than that of organic compound semiconductor materials. 

     p-n Junction inorganic semiconductor light-emitting diodes have been greatly developed, achieving coverage of the visible spectrum and emitting more light efficiency than incandescent bulbs. Inorganic LED devices have many advantages, such as strong structure, low driving power, long service life, high efficiency, strong stability and so on, and have been widely used. However, the production cost of inorganic LED devices is high, processing is difficult, low efficiency, light color is not easy to adjust. Organic compound semiconductors have been slow to develop, so high-end OLED (organic Light-Emitting Diode) displays remain highly priced