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LED ( Light Emitting Diode ), light emitting diode, is a solid-state semiconductor devices, it can direct the light into electricity. LED is the heart of a semiconductor wafer, the wafer is attached to a bracket, one end is negative, the other end is connected with the positive pole of a power supply, so that the chip package to be epoxy resin. Semiconductor chip is composed of two parts, a part is a P type semiconductor, it inside the hole-dominated, another end is a N type semiconductor, here is mainly electronic. But the two semiconductor link up between them, forming a " P-N junction. In some semiconductor pn junction, the injected minority carrier and the majority carrier recombination will make the excess energy in the form of light released, thus the direct conversion of electric energy to light energy. PN junction by applying a reverse voltage, minority carriers are difficult to inject, it does not light. This use of injection electroluminescent diodes is produced by the principle of light emitting diodes, commonly known as LED. When it is in a positive state (i.e. the plus ends of forward voltage ), LED current from the anode to the cathode, a semiconductor crystal emitted from the ultraviolet to the infrared light with different colors, the light intensity and current. The wavelength of light that is the color of the light, is formed by the P-N node of the decisions of the material.