Thinking about the current situation and existing problems of white LED

1, white LED status

At the end of the last century, the mature utilization of GaAIInP quaternary system and GaN materials led to the rapid development of white LEDs. By the beginning of this century, white LEDs have broken through the shackles of technology, and they have a variety of colors and realized Mass production. In addition, the introduction of organic vapor phase epitaxy and molecular beam epitaxy (MOCVD and MBE) in LED production has greatly improved the brightness and color saturation of LEDs. MOCVD technology is a material growth technology that can grow into a complete crystal with a single atomic layer thickness. At the same time, MBE is used in the material growth to realize the orientation control of the chip structure, which can be mass-produced. Complex structures such as multiple quantum wells. LEDs now have different colors, such as GaAllnP red, green, etc., while LEDs also have ultra-high brightness. In recent years, in response to the call of low-carbon economy, white LED has become an important light source with the advantage of high energy efficiency, and it has also attracted the attention of the semiconductor market. As a result, many cases of cooperation between LED companies and semiconductor companies have changed. Production mode of LED light source.

As early as more than a decade ago, the Chinese government launched the “National Semiconductor Lighting Project” program and began to explore semiconductor lighting technology in depth. Therefore, China's white LED industry began to introduce high-tech, and actively explored to break through the key difficulties and master the core technology as soon as possible. In the past ten years, China's white LED has achieved full color and ultra-high brightness, and has established a complete LED industry. At present, white LED has covered all fields of society. White LED has been closely related to people's lives. The function of white LED is not only lighting, but also an important component of many industries. The appearance of white LED appears in TV, mobile phone and car lighting. In the field of high-precision instruments, etc., the good development trend of white LEDs has been established.

2, the problem of white LED

2.1 The quality of white light needs to be improved, and it is necessary to standardize and improve parameter design.

The so-called white LEDs need to be adjusted in a variety of colors so that they emit the desired white light, and it is understood that the mixing ratio of the plurality of colors of light is very important. In order to ensure the quality of white light, some parameters are usually used for evaluation, such as color coordinates, color rendering index, and the like. If the mixing ratio of light is not properly designed, or the aging of devices such as chips, the white light of the LED may change, failing to meet the established design requirements, thereby affecting normal use. However, in fact, due to poor control of color temperature and color rendering index, it is easier for LED white light to not meet the requirements. In addition, since white LEDs are mostly used as illumination sources, it is necessary to improve design requirements, ensure the rigor of design, and thus control the illumination quality of white LEDs.

2.2 Luminous flux and luminous efficiency need to be improved, and high-power chips need to be designed.

In terms of luminous efficiency, white LEDs are more efficient than incandescent lamps, but their luminous efficiency is lower than that of fluorescent lamps and energy-saving lamps. In terms of luminous flux, white LEDs have less luminous flux, far lower than incandescent lamps, fluorescent lamps, and energy-saving lamps. . These problems limit the range of use of white LEDs, so white LEDs should be improved. First of all, it is necessary to improve the chip of the white LED, design a high-power type chip, and at the same time ensure the high quality and large size of the chip, so as to improve the internal quantum efficiency and thus increase the luminous power. However, the increase in luminous power will inevitably lead to an increase in heat, which in turn leads to accelerated aging of the chip. Therefore, it is necessary to deeply study the conversion of light energy and thermal energy. At the same time, since white LEDs are mostly used for assembling a plurality of LED bulbs, the heat of the LEDs is also gathered together, so that the heat dissipation problem of the LED assembly must be ensured, so as to ensure the improvement of the luminous efficiency and the stability of the white LED.

2.3 Working life needs to be improved, and it is necessary to enhance product reliability.

Although China's self-produced white LEDs have a long life, they are not much different from energy-saving lamps and cannot highlight the advantages of white LEDs. In theory, the life of white LEDs should be much higher than that of energy-saving lamps, but the actual life of LEDs does not reach the life expectancy. To this end, China's LED researchers should pay attention to optimizing product design and improving the actual life of white LEDs. There are many researches on the aging mechanism of white LEDs in foreign countries, which can provide some inspiration for LED design in China. At present, China's LED products tend to develop in the direction of high power, and the aging problem is also more serious, so the research on aging mechanism is more urgent.

2.4 Phosphors need to be improved, need to promote new products

Although China's white LED development is relatively fast, but due to the constraints of the design and manufacturing capabilities of Blu-ray chips, China's white LED products can only occupy the low-end market. In the design of blue chip, phosphor is an important luminescent substance, which is responsible for the blue light conversion of the chip into yellow light, and the luminous efficiency of the fluorescent chip of China's blue chip is not high. Therefore, in the process of promoting chip update and optimization, we must also pay attention to the selection of more stable phosphor quality to improve conversion efficiency. At present, ultraviolet-activated phosphors have been affirmed by researchers at home and abroad, and China can conduct research in this direction and develop new white LED products as soon as possible.

3, the conclusion

As an important semiconductor research achievement, white LED has a strong driving force for the development of China's lighting industry. Therefore, China needs to improve its chip design and manufacturing capabilities and promote the LED industry to become high-end. At the same time, China's semiconductor researchers must also actively research and discuss the problems existing in white LED technology, and strive to solve the problem of white LEDs as soon as possible, making China's LED technology a leader in the world LED industry.

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