Phosphor, commonly known as luminous powder, is usually divided into light-induced energy-storing luminous powder and radioactive luminous powder. Light-induced energy-storing luminous powder refers to phosphor that stores the light energy after being irradiated by natural light, sunlight, ultraviolet light and so on, and then slowly releases the light energy in the form of fluorescence after stopping the light irradiation. Therefore, the phosphor can still be seen glowing at night or in the dark, and can last for several hours to more than ten hours. Phosphors usually contain various types of transition metals or rare earth compounds. Phosphorescent materials are commonly used in CRT and plasma displays, fluorescent lamps, sensors and white LEDs.
Figure 1. The luminous principle of white LED
Figure 2. Phosphors of different colors