LED lights

LED (Light Emitting Diode) is a solid-state semiconductor device that can convert electrical energy into visible light, which can directly convert electricity into light. The heart of the LED is a semiconductor wafer,

One end of the wafer is attached to a bracket, one end is the negative end, and the other end is connected to the positive electrode of the power supply, so that the entire wafer is encapsulated in epoxy resin. A semiconductor wafer is made up of two parts, one is a P-type semiconductor, in which holes dominate, and the other end is an N-type semiconductor, which is mainly electrons on this side. But when these two semiconductors are connected, a P-N junction is formed between them. When an electric current is applied to the wafer through the wire, the electrons will be pushed to the P-region, where the electrons will recombine with the holes, and then the energy will be emitted in the form of photons, which is the principle of LED luminescence. The wavelength of light, which is the color of light, is determined by the material that forms the P-N junction.

At first, LED was used as an indicator light source for instrumentation, and later LED of various light colors was widely used in traffic lights and large-area display screens, resulting in good economic and social benefits. In the United States, for example, a 12-inch red traffic light was originally used as a long-life, low-efficiency 140-watt incandescent lamp, which produced 2,000 lumens of white light. After passing through the red filter, 90% of the light is lost, leaving only 200 lumens of red light. In the newly designed lamp, Lumileds uses 18 red LED light sources, which consume a total of 14 watts of power, including circuit losses, to produce the same light effect. Automotive signal lights are also an important area for LED light source applications.

For general lighting, people need a white light source more. In 1998, the development of a white LED was successful. These LEDs are made by encapsulating GaN chips and yttrium aluminum garnet (YAG) together. The GaN chip emits blue light (λp=465nm, Wd=30nm), and the YAG phosphor containing Ce3+ made by high-temperature sintering emits yellow light after being excited by this blue light, with a peak value of 550nm. The blue LED substrate is mounted in a bowl-shaped reflective cavity and is covered with a thin layer of resin mixed with YAG, about 200-500 nm. Part of the blue light emitted by the LED substrate is absorbed by the phosphor, and the other part of the blue light is mixed with the yellow light emitted by the phosphor to obtain white light. Now, for InGaN/YAG white LEDs, by changing the chemical composition of the YAG phosphor and adjusting the thickness of the phosphor layer, a variety of white light with a color temperature of 3500-10000K can be obtained. This method of obtaining white light through blue LEDs is the most widely used because of its simple structure, low cost, and high technical maturity.

Shortcoming:

LED lights are more expensive than other lighting fixtures. In addition, at present, the LED industry lacks unified standards, the quality of production products of various enterprises is different, and there are still many uncertainties in light efficiency, color rendering and life, but LED technology is also constantly improving, and I believe that one day LED technology will become more and more mature and enter the homes of ordinary people.