Semiconductor chip is composed of two parts, the part of the p-type semiconductor, in the dominant position it inside the hole, and the other end is the n-type semiconductor, here is mainly electronic. But when I connect the two semiconductor, a p-n junction formed between them. When a current passes through the wire act on the chip when electron is pulled into a p-region, electrons with holes in the p-compound then energy as a photon, which is the principle of LED lights glow. And the wavelength of the light is the color of the light, is decided by the formation of p-n junction of the material.
Initially LED as a light source for instrumentation, then various color of LED traffic lights and has been widely used in large-area displays, producing good economic and social benefits. With 12 inches of red traffic lights, for example, in the United States was using long-life, low luminous efficacy in 140-watt incandescent lamp as the light source, it produces 2000 lumens of white light. After the red filter light loss 90%, only 200 lumens of lights. In the light of new designs, Lumileds Corporation 18 red LED light sources are used, including circuit losses, total power consumption 14 w, you can produce the same luminous efficiency. Car lights are also important areas of application of LED light source.