Inventory of recent LED innovation technology progress [full text]

Dynamic semiconductor lighting technology as China's strategic emerging industries, energy-saving and environmental protection is of great significance, China is the world's semiconductor lighting products production, use and export of power. However, in the field of special LED light sources, due to the higher technical threshold, the market has been monopolized by foreign companies.

Recently, the team of Xiong Daxi, a researcher of the Optical Health Center of the Suzhou Medical Institute of the Chinese Academy of Sciences and the Suzhou Science and Technology Shikai Semiconductor Co., Ltd., won the "Technical Invention Award of the Chinese Optical Engineering Society" First prize.

Focus on the LED application market

Due to the huge market potential, LED-related industrial applications are rapidly expanding from general lighting to almost all fields. Different from general lighting, lighting applications in some special fields have also received more and more attention, and the market prospects are more and more optimistic. These applications need to rely on special LED light sources.

Xiong Daxi said that special LED light source is a kind of LED light source that pursues to emit more light energy in a small light-emitting area. It requires a single module with high electric power and power density, and the intensity is similar to that of laser. The special LED light source technology started around 2000, and the development is very slow. Domestic companies have almost no production, while abroad, only two high-tech starting companies, Osram and American Longminus, can provide it.

The reason is that there was no large-size vertical structure LED chip in China at the time. At the same time, special packaging technology, heat dissipation technology, optical design and integration technology were not enough.

Since 2009, in order to break through the monopoly of foreign manufacturers in this field, Xiong Daxi led the team with the strong support of the Chinese Academy of Sciences, Jiangsu Province, Suzhou City and High-tech Zone, focusing on the development and industrialization of special LED light sources. In R & D design and manufacturing technology, we made great breakthroughs by focusing on R & D and opening up new paths.

The research team has established technical advantages, and in conjunction with Suzhou Kekai Shikai Semiconductor Technology Co., Ltd., carry out industrialization work to provide solutions for ultra-bright high-density LED chip light sources.

Xiong Daxi said: "The special LED technology we developed focuses on LED applications and special markets, adopts different technical routes, has produced a series of technologies and cores, broke the monopoly of foreign products, and helped China in emerging subdivision fields abroad. Enhance the core competitiveness of the manufacturing industry. "

Unique LED chip light source technology

With the efforts of the R & D personnel, the scientific research team has broken through various obstacles and finally formed a technical route with independent intellectual property rights.

Daxiong Xiong said: "In response to the problem that special LED light sources require a large light emitting surface based on vertical structure chips, we have developed a" quasi-single chip "packaging technology, which uses a special process and uses a small size vertical structure chip to form a high-power package. Module. "

This technology can not only produce high light output on the same light-emitting surface, but also flexibly use small chips to expand the light-emitting area, thereby increasing the total light output.

"The high electrical power of the single module of the US Luminus is less than 150W, and the electrical power of our single module can reach more than 600W. The light source of foreign companies based on the single large chip technology, the light emitting surface is generally rectangular, and our chip emits light. The surface can be flexibly configured to match any shape with a specific optical system. "Xiong Xixi said. At present, products based on ultra-high optical density integrated packaging module technology have become the mainstream of the market.

In the previous special LED light source products, foreign manufacturers can only provide white light, or monochromatic light of one of red, blue, and green. Faced with the demand for spectrum in special fields such as biomedicine, the team has developed a multi-spectral high optical density module.

On the tiny 2.5 mm × 2.5 mm light-emitting surface, 16 wavelengths of narrow-band light can be integrated, and the wavelength of each light can be arbitrarily selected. This technology replaces mechanical control with electrical control, which greatly simplifies the structure of various optical instruments and brings revolutionary changes to a variety of biomedical instruments such as fluorescence microscopes and ophthalmological full-spectrum fundus detectors.

At the same time, the team also studied the base material of the high thermal conductivity vertical structure chip, the selection of the high thermal conductivity solid crystal material, the thickness control of the solid crystal layer, the baking temperature and time control, and the design of the packaging substrate. Based on these technical combinations, The thermal resistance of 600W module can be as low as 0.10K / W, which is in the global level.

Market segments are applied

Since the R & D work started in 2009, after years of improvement and accumulation, the products launched by the team have been gradually promoted in the market since 2010. At present, it has been widely used in some market segments, and some of them have become mainstream products.

"60% ~ 70% of the world's stage lighting is produced in China, with a total output value of tens of billions of yuan, and there are about 800 manufacturers. In the past, high-power density and high-power LED special light sources were mainly provided by American companies, and our products have been available since 2012. Entering the market, it has accumulated 200 customers, and American products have been marginalized. "Xiong Daxi said. Not only that, the projection display market, long-distance light projection and long-distance lighting market have all seen the presence of Suzhou Medical Laboratories.

In 2014, with the support of the "Bright Plan" of the Chinese Academy of Sciences, the team officially launched the development of ultra-long-range floodlights. Last year, the team successively developed projectile illuminators based on high-power and high-brightness LED light sources. Three of them have been successfully used in a logistics support force; mass-produced small LED searchlights have been used in bird-driving warning vehicles at Kunming Airport.

Xiong Daxi said: "Special LED light sources have begun to play an important role in modern molecular biology research and medical lighting, diagnosis, treatment and rehabilitation physiotherapy. Among them, light sources based on narrow-band multi-spectrum have been applied to multi-band fluorescence microscopes, small batch production in 2017 11 sets; a super-resolution structured light microscope based on a high-density special light source has been successfully developed, and the imaging quality and imaging speed have reached the international level, the cost is much lower than the competitors, and the market prospect is very broad. "

Now, the team is also aiming at the emerging direction of LED-based light health. Xiong Daxi told reporters that the research content of LED light health engineering includes photo-health defense, early prevention and detection of diseases, photo-treatment of diseases, rehabilitation and photo-health physiotherapy. In 2016, the National Key Laboratory of Semiconductor Lighting Innovation and the Suzhou Medical Laboratory established the Light Health Research Center in Suzhou, devoted to the development and application of special LED light sources in the field of light health.

"At present, the research group has developed a variety of infrared physiotherapy instruments based on infrared LED chips, including handheld and vertical, and horizontal models that are being processed and adjusted. Special LEDs are particularly suitable for home health care physiotherapy with their unique advantages. According to the size of China's population and the trend of population aging, the size of this market will reach hundreds of billions. "Xiong Daxi said.

Micro LED may help deaf patients find their hearing

A cochlear implant is an electronic device that converts sound into an electrical signal in a certain encoded form by an external speech processor, and directly excites the auditory nerve through an electrode system implanted in the body to restore or reconstruct the hearing function of the deaf. However, due to the current spread around the electrodes, the cochlear implant's resolution for complex sounds is still very low.

Recently, researchers such as Christian Robel of the Institute of Auditory Neuroscience and the Inner Ear Laboratory of the Medical Center of the University of Göttingen in Germany have developed an optical cochlear implant using optogenetics technology.

Researchers in mice have discovered that this cochlear implant can use light to stimulate the auditory nerves of deaf mice. They used viral vectors to introduce a light-sensitive protein into the cochlear neurons. After implantation, they stimulated the auditory pathway of deaf mice and restored their hearing ability. This optical cochlear implant shows the potential for high resolution of complex sounds.

At present, the research team only uses one light wave, and the next step will be to develop a device that can manufacture multiple light waves. The device design may use Micro LED array or waveguide technology to guide the light generated by the optical fiber.

Professionals pointed out that LED is a better choice, but the light is relatively blurred and requires a technical breakthrough.

LED technology provides possibilities for treating cancer

In addition to display and lighting, the application of LED technology in the medical field is also constantly improving. Research has found that LED technology has created possibilities for the treatment of cancer.

It is reported that researchers at Waseda University in Japan have developed an implantable device composed of LED chips and bioadhesive nanosheets, which can successfully shrink tumors in mice through photodynamic therapy. The research results have been published in the Nature Biomedical Engineering journal on July 16, 2018.

Rhythm photodynamic therapy is a long-term treatment method that uses low-dose special drugs and special lighting to kill cancer cells. To adopt rhythm photodynamic therapy, the researchers designed the implantable device on the inner surface of animal tissue, where the device can release low-intensity radiation to treat targeted lesions, thereby achieving therapeutic goals.

The research team said that compared to traditional photodynamic therapy, the device reduces the light intensity by a factor of 1,000, which can avoid damage to normal tissues and effectively treat tumors. According to the research team leader Toshinori Fujie, surgery or radiotherapy for cancerous tumors in the body such as the brain or pancreas are risky, and implantable devices may play an important role in the treatment.

Specifically, by installing the rhythm photodynamic therapy device directly at the target lesion, the threat to the healthy area can be reduced.

New white LED luminous efficiency hits record

According to a recent report from the American Daily Science website, Turkish scientists have developed a new type of white light-emitting diode (LED) with a luminous efficiency of a record 105 lumens / watt. The researchers said that with further development, the efficiency of this LED can reach more than 200 lumens / watt, is expected to show their talents in the field of homes, offices, etc., to achieve more energy-saving and environmentally friendly lighting.

The new LED is manufactured using a commercially available blue LED combined with a flexible lens filled with a solution of nano-semiconductor particles called quantum dots. The light emitted by the blue LED causes the quantum dots to emit green and red light. It combines with blue light to produce high-quality white light with color temperature and optical characteristics.

Turkish scientists have manufactured white LEDs based on nanomaterials.

The researchers explained that quantum dots have many advantages in the manufacture of white LEDs: they are easy to manufacture; they can change their light emission color by increasing the size of semiconductor particles; and changing the concentration of doped quantum dots can control the characteristics of light.

In order to manufacture such LEDs, quantum dots that can convert blue light into red or green light are needed. To this end, they carried out more than 300 synthesis reactions and obtained quantum dots that can emit different colors of light and perform well. They mixed cadmium, selenium, zinc, and sulfur at a high temperature to make a quantum dot solution, which filled the gap between the lens made of silicone resin and the LED chip. Silicone lenses are elastic, so no leakage occurs when the solution is injected, and the transparency of the material ensures that the necessary light can pass through.

At present, researchers are working to improve the efficiency of LEDs and hope to use environmentally friendly cadmium-free and lead-free materials. They also plan to study liquid LEDs under different conditions to ensure their long-term stable use.

The head of research, Saidat Nizamoglu of the University of Cork, said: "The efficiency of new LEDs is higher than other white LEDs based on quantum dots. Moreover, the methods of manufacturing quantum dots and synthesizing new LEDs are simple and cheap. It is suitable for large-scale production. If LEDs with an efficiency of 200 lumens / watt can be used to replace traditional lighting sources, the global lighting power consumption will be reduced by more than half, and greenhouse gas emissions will be reduced by 200 million tons. "

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Green LED bulbs reduce the chance of accidentally catching conservation species

A multinational research team led by Dr. Jeffrey Mangel of the University of Exeter, UK, released a new research report, pointing out that if LED bulbs powered by green energy batteries are used on fishing nets, the probability of seabirds and marine life getting caught in fishing nets will be reduced by more than 85 %.

The research team conducted experiments in the sea area of ​​Sechura Bay in northern Peru. From the evening, the net was cast until the next morning when the net was harvested. 114 groups of fishing nets were placed in the sea and fixed. Each group had two fishing nets, one of which was along the fishing net floating rope. One LED bulb was installed in the meter, and another LED bulb was not installed as a control group.

As a result, it was found that fishing nets equipped with LED bulbs had a much lower chance of being caught in "South American Cormorants" than fishing nets not installed. South American cormorants are endemic to the local area and can dive into the water for fishing, but they are often trapped on fishing nets.

The research was published in the journal "Society Open Science". Dr. Mangel said the results show that humans can enable fishermen to work at a low cost while reducing the chance of accidentally catching other conservation species.

Previously, the research team had done similar experiments. At that time, they also divided the fishing net into an experimental group with green LED bulbs and a control group without LED bulbs. The results showed that the probability of the turtle being caught was reduced by 64%, and there was no Affect the catch.

The research team is now actively expanding cooperation with Peruvian fishermen and wants to test whether different colors of light can achieve the same effect on different conservation animals.