With the increasing awareness of environmental protection, the problem of high power consumption and waste pollution of traditional lighting equipment has received increasing attention. Low power consumption and waste recycling have become the active direction of environmentally friendly light sources. White LEDs, which are known as â€œgreen lighting sourcesâ€, are in line with people's environmental standards, and this environmentally friendly light source may be completely replaced in the past decade. Existing bulb lighting products.
LED is a solid-state semiconductor device that can convert electrical energy into visible light. Unlike ordinary incandescent bulbs, which use heated illumination, LEDs use cold-lighting technology, which generates much lower heat than ordinary lighting fixtures. White LED has a series of advantages such as low voltage, low power consumption, high reliability and long life. It is a green lighting source that is environmentally friendly and energy efficient. The huge market demand and the significant economic and social benefits have enabled the world to invest a lot of financial, human and material resources to promote the research and development of solid white LEDs as solid-state lighting sources, and set up specialized agencies to set strategic goals. And plans to ensure that the development of solid white LEDs is leading the way.
LEDs are mainly divided into visible light and invisible light. The visible light spectrum has a wavelength range of 380 nm to 760 nm, which is a seven-color light that can be perceived by the human eye - red, orange, yellow, green, cyan, blue, and purple, but each of the seven colors of light is a monochromatic light. It is mainly used for backlights, automotive lighting, etc., and invisible LEDs include IrDA, VCSEL and LD, etc., which are widely used in communication.
For general lighting, people need a white light source. Therefore, white LED is the most promising LED emerging product, and is optimistic in the industry. In the next ten years, it will completely replace the existing lighting products and become a new lighting device.
In the 1960s, scientists and technicians used the principle of semiconductor PN junction light to develop LED light-emitting diodes. The LED used at that time was made of GaASP, and its color was red. After nearly 30 years of development, LEDs have been able to emit red, orange, yellow, green, blue and other color lights. However, the white LEDs needed for lighting have only developed in recent years.
Technical overview of white LED
Since white light is not monochromatic light, but a composite light composed of a variety of monochromatic light, in order for the LED to emit white light, its spectral characteristics should include the entire visible spectral range. According to people's research on visible light, we can see that white light requires at least two kinds of light mixing, that is, two-wavelength light (blue light + yellow light) or three-wavelength light (blue light + green light + red light) mode. Both modes require blue light, so ingesting blue light has become a key technology for making white light.
At present, most of the white LEDs on the domestic market are domestic LED manufacturers that use imported blue LED chips and phosphors to package themselves. Due to the weak technical strength and independent development capability, the selection of blue chip and the performance of white LED are limited and affected. Therefore, there is still a process for the promotion and application of white LEDs.
At present, the way of emitting white light can be mainly divided into two types, one is single crystal type, that is, blue light plus yellow fluorescent powder or ultraviolet light LED plus RGB three-wavelength fluorescent powder to generate white light. The other is a polymorph type, that is, white light is formed by using two complementary colors or mixing the three primary colors. The driving voltage, the light output, the temperature characteristics and the lifetime of different LEDs are different. The polymorphic method has many factors to be controlled, and the cost is also high. The single crystal type uses only one element. Yes, and the design on the drive circuit will be easier. Therefore, most manufacturers are more inclined to do the research and development in the way of single crystal.
The application prospect of white light LED new light source is diversified
Color mobile phone market
At present, the largest application market for white LEDs is the backlight of color mobile phone screens and buttons. Each color mobile phone screen backlight requires about 2-3 white LEDs. For each mobile phone, the buttons must use high-brightness LEDs on average about 8- 12, due to cost considerations, the current proportion of white LEDs is still low, it is estimated that in the future, under the influence of falling prices of blue and white LEDs, the market share of yellow-green LEDs will decline, which will benefit the increase in demand for white LEDs.
Camera phone and digital camera flash market
The flashlight for camera phones provides a new application market for white LEDs. At present, each camera phone needs about 3-4 white LEDs as the flash light source. With the increase of the proportion of camera phones, the white LED flash market has grown rapidly. . As for digital camera flash, most of them are still based on xenon flash. However, with the demand for power saving and light and thin design, digital camera manufacturers will increasingly use white LED as the source of flash.
Backlight market for LCD panels
Since 2006, the use of mercury-containing CCFL (cold cathode tube) related products has been banned, making white LEDs the main backlight source in the future, but the cost of LED backlight modules is still high, and the luminous efficiency still needs to be improved. Therefore, before solving the above bottleneck problem, the backlight of the medium and large size panel is still dominated by CCFL.
Automotive lighting market
Considering the safety of driving the car, the light source for the car, especially the exterior lighting, has higher requirements for the luminous efficiency of the white LED. Therefore, it is still a niche market, but the interior lighting such as the interior reading lamp, dome light, decorative light, etc. It is expected to become its main application market.
General lighting market
The main light sources in the general lighting market are fluorescent lamps, incandescent lamps, halogen lamps, etc. The market share is 42%, 27%, and 17%, respectively. Compared with the above-mentioned light sources, white LEDs have the advantages of energy saving and small size. At present, the luminous efficiency of the white LED light source has reached 40 lm / W, which has exceeded the incandescent lamp (7.4 ~ 16 lm / W). But to replace the fluorescent lamp (40~70lm/W) into the general lighting market, its light efficiency needs to reach 150lm/W. At the same time, it also needs to solve the problems of low luminous brightness, high cost and poor color rendering index. To this end, people are working on three major factors: chip, phosphor and package to further improve chip quality and structure, improve internal quantum efficiency, optimize light extraction rate, reduce color temperature, and strive to achieve large-scale semiconductor illumination at an early date.
to sum up:
White LED technology still has a lot of room for development. White LEDs have higher luminous efficiency, low power consumption, long life and environmental protection, which will bring more markets. The application of LED white light in the automotive and lighting market is growing very fast, and the future of white LED market is promising.
(Edited from: Gaogong LED Editor to Peach)
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