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Using LED light source for lighting instead of power consuming incandescent lamps, and then gradually entering the entire lighting market will save a lot of power. Recently, the white LED has reached a single power consumption of more than 1 watt and light output of 25 lumens, which also increases its practicability.
Fifty years ago, people already knew the basic knowledge that semiconductor materials can produce light, and commercial diodes were produced in 1960. LED is the abbreviation of LightEmitting Diode (Light Emitting Diode). Its basic structure is a piece of electroluminescent semiconductor material, placed on a shelf with leads, and then sealed with epoxy resin around to protect the internal core wires. Therefore, LED has good seismic performance.
The LED can change color by changing the current, and can easily adjust the energy band structure and band gap of the material through chemical modification to achieve red, yellow, green, blue and orange multi-color luminescence. For example, if the LED is red at low current, it can turn orange, yellow, and then green with the increase of current.
The price of LED is relatively expensive. Compared with incandescent lamps, the price of one LED can be equivalent to the price of several incandescent lamps. Usually, each group of signal lamps needs more than 300~500 diodes.
Table 1 lists the current types of white LEDs and their luminous principles. It can also be seen from the table that some kinds of white LED light sources cannot be separated from four kinds of phosphors: three primary colors of rare earth red, green, blue and garnet structured yellow. In the future, three wavelength light is more promising, that is, inorganic ultraviolet light crystal plus R G. B Three color phosphor is used to encapsulate LED white light. It is expected that three wavelength white LED will have commercial opportunities. However, the particle size requirements of the three primary phosphors here are relatively small, and the stability requirements are also high. The specific application is still under exploration.
In recent years, the research and development achievements of white LED: In September 2008, Philips Lumileds and Osram Opto Semiconductors published 140.1 lm/W and 136 lm/W respectively, and produced 138 lm and 155 lm (lumens) respectively. They both use 1mm sized chips and drive them under 350mA; Cree, an American LED manufacturer, announced that its white light emitting diode has achieved 161lm/W. Visible, white LED has an attractive prospect in terms of high luminous efficiency and high lighting
