A, LED history
50 years ago people have to understand semiconductor materials can produce light of the basic knowledge, in 1962, general electric (ge), Nick He Lun ark (NickHolonyakJr.) developed the first practical application of visible light leds. Leds are English light emitTIng diode (LED), its basic structure is an electroluminescent semiconductor materials, placed in a wire rack, then sealed with epoxy resin around, namely solid encapsulation, so can protect the internal core, so the LED seismic performance is good.
Initially LED is used as the indicator light instrument and then all kinds of light color of LED traffic light and display screen has been widely applied in large area, produced good economic and social benefits. 12-inch red traffic lights, for example, in the United States could have been used long life and low light efficiency of 140 - watt incandescent lamp as light source, it produces 2000 lumens of white light. After the red filter, light loss 90%, only 200 lumens of red light. And in the light of the new design, Lumileds companies adopted 18 red LED light source, including circuit loss, total power consumption of 14 watts, can produce the same light. Car light is also an important field of LED light source.
Second, the principle of the LED chip
LED (Light EmitTIng Diode), light-emitting Diode, is a solid-state semiconductor devices, it can be directly put DianZhuan into Light. The heart of the LED is a semiconductor chip, chip attached on a bracket, at the end of the end is negative, the other end connected to the power of the anode, the whole chip is encapsulated by epoxy resin. Semiconductor chip consists of two parts, one part is a p-type semiconductor, dominated by holes in it, the other end is n-type semiconductor, here is mainly electronic. But this two kinds of semiconductor connected, between them to form a p-n junction. When a current flows through a wire to the chip, the electron will be pushed P area, electron and holes in the P zone compound, then will be issued in the form of photon energy, this is the principle of LED. And the wavelength of light was the color of the light, is determined by the formation of p-n junction material.