The core of the light-emitting diode is composed of p-type semiconductor and n-type semiconductor chip, between the p-type semiconductor and n-type semiconductor has a transition layer, called p-n junction. In the PN junction of some semiconductor materials, the injection of minority carriers and the majority of carriers recombine the excess energy will be released in the form of light, so that the energy directly converted to light energy. PN junction plus reverse voltage, a small number of carriers is difficult to inject, so do not light. The use of injection-type electroluminescence principle of the manufacture of the diode called light-emitting diodes, known as LED. When it is in the positive working state, the current flows from the LED anode to the cathode, the semiconductor crystal from the ultraviolet to infrared different colors of light, the intensity of light and current.