In addition to general lighting, what are the ways for LEDs?

LED has been promoted in the lighting market since its inception, with its low energy consumption, small size, long life, no pollution, fast response, low driving voltage, strong shock resistance and high color purity. A generation of lighting sources and green light sources. In recent years, the general lighting market has become increasingly saturated. What are the ways for LEDs to be used outside of general lighting?

The LED market with hundreds of flowers

LED just came out At the time, due to insufficient power and insufficient color, it was only applied in scenes such as billboards and traffic lights. With the advancement of technology, the application of LEDs on the backlight display has led to an explosive growth in the market for LED displays, and the emergence of white LEDs has also opened up the general lighting market. After years of hard work, these fields have become saturated. Special lighting such as automotive lighting, flashlights, and medical treatments have gradually entered the public eye and become a new direction in the LED field. The LED lighting market is showing a hundred flowers.

Hong Kong University of Science and Technology Shenzhen Research Professor Li Shizhen of the hospital

In addition to lighting, LEDs are also promising in many non-illumination fields. At the “OFweek (fifteenth) China LED Lighting Industry Development Summit Forum held on November 13th, Professor Li Shizhen from the Shenzhen Research Institute of the Hong Kong University of Science and Technology introduced the technology trends of LED in the field of non-lighting. Professor Li Shizhen believes that applications that are not related to human vision are non-lighting applications. These include plant lighting, visible light communication (VLC), and applications for invisible bands. Among them, plant lighting can be extended to animal husbandry and aquaculture, in addition to agricultural and horticultural applications. VLC technology can complement the WIFI to a certain extent by virtue of its security, economy and confidentiality. It can also be combined with lighting applications to expand into other application scenarios, such as environmental monitoring.

For non-lighting applications, the prospects and applications of invisible light are no doubt broader. So what are the applications of infrared LEDs and UV LEDs?

Application of IR/UV LEDs

In accordance with Professor Li Shizhen, the application of IR/UV LEDs It already exists, but its marketization is still in the initial exploration stage. It is still a blue ocean market. It is still far from the mass production and the inflection point of the outbreak of the industry. There is also a lot of room for improvement in technology.

He believes that most of the current IR LEDs are used in the military and other special fields, but will be extended to the public in the future. The future of IR LEDs will be locked into portable products for night vision, pupil recognition, heartbeat detection, cosmetic beauty and biomedical applications. In contrast, UV LEDs will be used more in the industrial sector and will be much larger than IR LEDs in terms of market size.

The wavelength range of ultraviolet light is 200nm-400nm, and these different wavelengths of UV light application scenarios are also different, so it is divided into UVA (320nm-400nm), UVB (280nm-320nm) and UVC. Three types (200nm-280nm). UVA is mainly used for polymer curing, such as printing ink drying, nail polish second drying, 3D printing fast curing. UVB is mainly used in biomedical applications such as dermatological treatment. UVC is mainly used for the disinfection of gases and fluids.

Research status and R&D difficulties

In LED research In terms of aspects, universities and research institutes at home and abroad have different priorities. International research focuses on new materials, while domestic focus is on LED packaging. For the development of domestic LED, Professor Li Shizhen believes that the most critical issue is the mentality problem. From material development to packaging structure to process optimization, it is a long process of continuous research and continuous investment. To do research, you must first find the right position, sink your heart, and move forward slowly.

The development of LEDs from the visible to the invisible band is not just a matter of changing a chip. Taking UV LED as an example, compared with visible light LED, there are three major problems in the development of UV LED, namely epitaxial growth equipment, chip material, and LED package. UV LEDs have higher requirements for MOCVD uniformity, temperature tolerance, etc., and the epitaxial growth conditions of visible light LEDs are not applicable. In the past, blue LEDs used GaN or indium gallium nitride as the substrate, while UV LEDs required aluminum gallium nitride as the substrate. The lattice defects and adaptation of the two were different, and they needed to be re-examined. The packaging system is also very different from the traditional packaging, and it needs to be re-developed.

At present, Professor Li Shizhen’s research group has realized the development of UVA LED packaging materials and structures. He said that the previous concept holds that silver is the best reflective layer material, but for the ultraviolet band, aluminum is much better than silver. The reflectivity of aluminum to different wavelengths is relatively constant, and is still stable after heat aging treatment, while the reflectance of silver varies with wavelength and cannot be stabilized after heat aging treatment. In order to ensure the stability of industrial design, his research group chose silver as a reflective layer to achieve good results. In addition, the UVC below 280 nm is basically a metal or ceramic package, which is not only expensive but also bulky. How to replace the traditional package with plastic packaging is a research direction.

Requires scientists and engineers.

At present, China’s optoelectronic talents are in short supply, and market demand is strong, and universities are carrying the responsibility of cultivating talents. Professor Li Shizhen believes that the current lightThe electronics industry lacks a large number of technical talents, and colleges and universities should focus on allowing students to “learn and apply”. Now many students are lost after they finish school, and they forget when they finish the exam. This is not unrelated to the disconnect between the school and the industry. To this end, Professor Li introduced the concept of the Hong Kong University of Science and Technology.

The HKUST also attaches great importance to cooperation with enterprises and the combination of production and research. HKUST advocates that professors participate in industrial projects. For example, they cooperate with Huawei, Zhouming Technology, Ruifeng Optoelectronics and other enterprises to provide support for enterprises. On the one hand, they also use enterprises to enhance students’ understanding of the industry and enable students to graduate after graduation. Quickly integrated into the enterprise’s echelon. In terms of teaching recruitment, it is also more inclined to hire professors with several years of industry experience. Such professors can transfer some relevant knowledge in the industry, whether they are teaching or guiding students. This is good for student development and industrial development. . Of course, the school also has a highly sophisticated team. The goals of these teams are in research, and for engineering schools, they are more focused on learning.

In addition, the layout of many disciplines of HKUST is not in the direction of the depths, but in the direction of Guangbo. The establishment of a large number of interdisciplinary subjects, in addition to teaching students’ professional knowledge, can also be extended to related fields in the surrounding areas. There is an evaluation indicator in the doctoral thesis defense of HKUST. In addition to the content of the paper, it is sufficient to understand other relevant fields involved in the same large field.

Hong Kong University of Science and Technology Shenzhen Research Institute

Professor Li Shizhen Said: “In the field of pure scientific research, we need a very specific and very deep professional accumulation. This part belongs to people who create knowledge and are at the top of the pyramid. But this can only be a small group of people, a small part is extremely intelligent and extremely talented. The proportion of people in the middle and lower levels of the pyramid is much higher than that of the spire. What they need to do is to transfer and apply knowledge. For this group of people, after mastering the basic professional knowledge, they should go to the broad and problem-solving problem. Direction to develop.”

Where is the LED lighting road?

In the past ten years, the basic idea of ​​LED is to replace, just to put the traditional light source The replacement of the light source into an LED makes many of the characteristics of the LED not reflected. In the future, with the upgrading of architectural design, there will be more and more light sources designed specifically for LED size specifications, hidden, or flat-panel, instead of the traditional lamp holder design.

LED has the characteristics of small size, low power consumption and responsiveness. These features have many application scenarios to be developed, and the market space in this area is very broad. Although the current replacement market is still large, the profit margin is already low, and it is difficult to increase the added value of the product. For the LED industry practitioners, we should try our best to use the imagination of LED technology to develop new application scenarios, find the edge that can reflect the advantages of LED, and open the next application door of LED.

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