LED, a light emitting diode, is a solid-state semiconductor device that converts electrical energy into visible light. The heart of LED is a semiconductor wafer, one end of which is attached to a support, one end is a negative electrode, and the other end is connected with the positive pole of the power supply, so that the whole chip is encapsulated by epoxy resin.
The semiconductor chip is made up of two parts, one part is the P type semiconductor, in which the hole is dominant, the other end is the N type semiconductor. But when these two semiconductors are connected, they form a P-N junction. When the current through the wire acting on the chip, the electrons will be pushed to the P area, in the P area of the electronic and hole compound, and then will be issued in the form of photons of energy, which is the principle of led corn light emitting. The wavelength of light is the color of light, which is determined by the material that forms the P-N junction.
Used for the first LED light source instrument, but all kinds of light colored LED has been widely used in traffic lights and large screen, resulting in good economic and social benefits. The 12 inch red traffic lights as an example, in the United States was long-lived, 140 watt incandescent lamp with low luminous efficiency as a light source, it produces 2000 lumens of light. The red filter, the light loss of 90%, only 200 lumens of light. In the new design of the lamp, Lumileds uses 18 red cheap led corn light source, including circuit losses, including a total power consumption of 14 watts, can produce the same light effect. Automotive signal light is also an important area of LED light source applications.
For general lighting, people need a white light source. 1998 white light LED development success. This LED is the GaN chip and yttrium aluminum garnet (YAG) package together. GaN chip emits blue light (lambda p=465nm, Wd=30nm), made of high temperature sintering of Ce3+ containing YAG phosphor by the blue light emitted after the yellow light, the peak 550nLED lamp M. Blue chip installed in the LED based wanxingreflection in the cavity covered with a resin mixed with thin films of YAG, about 200-500nm. The blue light emitted by cheap led corn light substrate is absorbed by the phosphor, and another part of the blue light and the yellow light emitted by the phosphor powder can be mixed with white light.
The InGaN/YAG white LED, YAG phosphor by changing the chemical composition of the phosphor layer and adjust the thickness of the 3500-10000K color temperature can be colored white. The method of obtaining white light by led corn light has the advantages of simple structure, low cost and high technical maturity online.