Compared with traditional incandescent lamps, photodiodes have several advantages.

　　First of all, the photodiode has no filament, which eliminates the possibility of burnout, so it has a longer service life.

　　 In addition, the small plastic bulb of the photodiode makes the photodiode more durable. Today's electronic circuits are also easier to use. The light-emitting process of conventional incandescent lamps contains a lot of heat, which is a waste of energy. If you don't use the lamp as a heater, most effective current will not directly produce visible light. The heat emitted by the photodiode is very small. Relatively speaking, the more electric energy directly emits light, which greatly reduces the demand for electric energy.

　　 So far, photodiodes are still too expensive for most lighting applications due to the use of advanced semiconductor materials. In the past 10 years, the price of semiconductor devices has fallen sharply. However, in a wider range of applications, photodiodes are a more cost-effective lighting option. In the near future, photodiodes will play a greater role in world technology.

　　LED is made of PN structure like ordinary diodes and has unidirectional conductivity. After adding a forward voltage to the photodiode, the holes injected from the p region into the n region and the electrons injected from the n region to the p region are in the vicinity of the PN junction with the electrons in the n region and the holes in the p region respectively. Compound, produce spontaneous emission light. According to the different semiconductor materials, the energy states of electrons and holes are also different. The energy released when electrons and holes recombine is different. The more energy released, the shorter the wavelength of light emission. Commonly used are red, green or yellow diodes.