Importance of white LED: It has a wide range of applications, especially as a new light source - the fourth generation lighting source, which will produce tremendous energy-saving effect in the future. White LED have many advantages: solidification, small size, long life (10,000 hours), anti-seismic, not easy to be damaged, fast start-up response time (nanoseconds), low power consumption, no pollution (mercury) and so on.
Principle and scheme of producing white LED
Simply speaking, there are three principles to produce white LED:
Blue LED chips and yellowing phosphors which can be effectively stimulated by blue light are organically combined to form white LED. Some blue light is absorbed by phosphors, which stimulate phosphors to emit yellow light. By mixing the emitted yellow light with the remaining blue light, the white light with various color temperatures can be obtained by adjusting their intensity ratio.
White light can also be obtained by combining red, green and blue LED into a pixel.
Like the three-color energy-saving lamp, the ultraviolet LED chip and the red, green and blue three-color fluorescent organically combine to form a white LED, which can be effectively stimulated by ultraviolet light.
Light Efficiency and Photoelectricity of White LED
According to the analysis of theory and technology development, the light efficiency of white LED can reach more than 2001m/w. The light efficiency of high power white LED
can be increased six times in just five years. The chart shows that the light efficiency of white LEO has increased and expected development from 1998 to 2002.
At present, people divide the development of white LED into two phases: 2005 and 2010. After 2005, white LED began to replace incandescent lamps and become commercial lighting; in 2010, it became home lighting. There are two problems that must be overcome to achieve this target.
Cost must be reduced to US $0.01/lm.
It is necessary to improve light efficiency and light transmission.
The answer is yes. Blue and ultraviolet LED chips, LED package
(including phosphor coating process) and phosphors are being improved. For chips:
Developing large-scale chips, such as Cree's recently launched 0.15W blue-light 900900900um large-scale chips;
Manufacturing high-power chips. 5W chips have been introduced to the market, which is much ahead of the expectation of the 2000 Strategic Seminar.
The new chip inversion technology improves the external quantum efficiency.
Actively develop ultraviolet LEDs with shorter wavelength, so that there will be many tricolor phosphors with higher efficiency than YAG: Ce phosphors currently used, which will achieve a new level of white LED.