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(Organized by LEDinside China Team)
As 2016 comes to an end, there were many exciting and surprising technology breakthroughs, based on statistics complied by LEDinside there were at least 10 major technology advancements this year.
American researchers make droop free LEDs
Researchers from the University of Illinois at Urbana Champaign developed a new method of making brighter and more efficient green LEDs this year. Using an industry-standard semiconductor growth method, the gallium nitride (GaN) cubic crystal was grown on silicon substrate to produce a powerful green light for solid-state lighting.
"This work is very revolutionary as it paves the way for novel green wavelength emitters that can target advanced solid-state lighting on a scalable CMOS-silicon platform by exploiting the new material, cubic gallium nitride," said Can Bayram, an assistant professor of electrical and computer engineering at Illinois
Usually, GaN forms into one of the two crystal structures: hexagonal or cubic. Hexagonal GaN is thermodynamically stable, and the conventional form used in semiconductor applications. However, the hexagonal form GaN is more prone to polarization, where internal electric field separates negatively charged electrons and positively charged holes, preventing them from combining, hence reducing light output efficiency.
Bayram and his graduate student Richard Liu’s research introduced a cubic form of GaN crystals, which they believe can make LEDs with zero droop. For green, blue or UV LED, the light-emission efficiency generally declines with higher current input, which is characterized as “droop.”
Related article for further reading: Researchers Make Green LEDs Brighter and More Efficient
Ostendo Epilab launches world’s first full color GaN-based LED
Based in Carlsbad in Southern California, Ostendo EpiLab launched the world’s first RGB LED. The LED based on GaN technology uses three specific materials to construe a quantum structure to emit different color lights, the color LEDs can be emitted independently or mixed. Conventional LEDs typically are monochromic, and can only emit a single wavelength. To achieve colorful RGB lighting effects, more than one LED is required to mix the desired color.
The color is determined by the phosphor coating or substrate material used for the LED. Only a handful of researchers have attempted to make a single LED chip capable of emitting full range of RGB colors.
Ostendo develops next generation Solid State Lighting (SSL)-based display technologies and products for commercial and consumer markets with the objective to achieve efficiencies and cost effectiveness at the material, the device and the system levels. Ostendo's enabling technologies support products that are disruptive in their individual marketplaces.
Advancements in UV LED curved lens technology
Integration Optic Technology Institute of Chongqing Institute of Green and Intelligent Technology at China Academy of Sciences announced new advancements in UV LED curved lens technology, which can be applied in light sources of UV exposurers, PCB, LCDs, and even in touch panel applications. The Chinese research institute has been granted the UV LED lens patent CN203642076U, and highly uniform UV LED for exposurer CN201420651432.4.
Conventional collimated exposure machine use high pressure mercury lamp since light sources have very short lifespans of 1,000 hours, high power consumption and is a pollutant. UV LEDs used to replace mercury lamp sources have a lifetime nearly 50 times of the mercury lamp, and can slash energy consumption by 90%, substantially lowering production costs and lowering environmental pollution.
The research institute has made a significant breakthrough in multiple curved surfaces in LEDs for precise lighting, which is suitable for UV wavelengths and non-organic optic component processing and other key technologies. The initial phase of development is based on UV LED collimated exposure machine, the collimation half-angle can be controlled within ±2°, and the uneven lighting distribution smaller than 3%, while light intensity can reach 40 mW/cm2.
Saphlux develops new technology to solve issues Shuji Nakamura is wrangling with
Founded in 2014 by Professor Jung Han from Yale University, GaN material provider Saphlux finally was able to offer a new solution in early 2016. The company declined to reveal details because it involves confidential business information, and was finally able to break free from conventional semi-polar GaN material growth models. The company has been able to offer standard large sized sapphire substrates that can be directly used to grow semi-polarized GaN, and control the crystal growth direction plus shape.
This technological breakthrough indicates the industry will be able to solve the bottleneck of quantum droop, and green gap of first generation LED materials to make highly efficient LEDs and laser products. This is a significant breakthrough for luminaires with high product requirements such as medical and outdoor lighting.
Significantly raising white LEDs lumen efficiency with innovative materials
Researchers from National Tsing Hua University in Taiwan, recently published a paper in scientific journalACS Nano, where they successfully made a white LED product made from Alrali earth metal rather than rare earth metals. The LED is basically made from Alrali earth metals, combined with metal organic frames (MOF), graphene and other materials on the top and bottom layer to make a white LED. The LED made from new materials can emit light beams with similar quality to natural lights, and does not emit strong blue light. The lumen efficiency is significantly improved, because it does not have to filter out other colors.
Typically, LEDs are blue light emitting semiconductor chips that require a yellow phosphor coating to convert light beams into white, but this more or less reduces lumen efficiency.
LEDs typically emit blue light, and convert the light to white through yellow phosphor, which reduces lumen efficiency.
Japan develops rare element free red LEDs
Tokyo Institute of Technology and Kyoto University jointly announced their findings in developing a red light emitting semiconductor that does not use costly rare elements, reported Kyodo News.
The researchers are turning to earth-abundant elements as an alternative, such as using nitrogen and zinc components as criteria for their screening methods. The low cost materials can reduce the production costs of red LEDs and solar cells.
Researcher finds hybrid nanocrystal LED designs can effectively suppress efficiency droop
Nanjing University researchers found a new application for hybrid nanocrystals, where it can be used to fill holes in InGaN or GaN LED structures to significantly boost white LED lumen efficiency.
The findings were published in Applied Physics Letter, which noted the key to raise Color Conversion Efficiency (CCE) is determined by effective non-radiative resonance energy transfer rather than integrating blue light emitted by the InGaN or GaN LED, or down conversion materials for instance phosphor or even nanocrystals, where down conversion radiation often occurs.
Nanjing University of Technology develops most efficient perovskite LED
A research team headed by Wei Huang of Jiangsu Flexible Electronic Laboratory, and Professor Jiangpu Wang’s significant breakthroughs in perovskite LED research. They introduced a perovskite with multiple quantum well structure for LEDs, and the component’s efficiency and reliability far exceeded other perovskite LEDs.
Perovskite is a light emitting material that kicked off a new research direction, and only by deepening the research foundation can the technology be commercialized in the future.
Wacker Chemie launches new adhesives for LED packages
Munich-based Wacker Chemie successfully developed two types of silicon LED encapsulation compounds, respectively LUMISIL740 and LUMISIL770. The LED package material can be cured to form highly transparent silicone elastomers, flexible silicon form. Both silicones can withstand extremely high working temperatures and strong light radiation without yellowing or embrittlement. The LEDs are suitable for encapsulating high performance LEDs.
The new LED encapsulants LUMISIL 740 and LUMSIL 770 are two-component systems that can cure at room temperature using a platinum-catalyzed addition-reaction. The cured rubber grades has a refractive index of 1.41, which is generally found in polydimethylsiloxanes. The two products belong to the group of normal refractive index (NRI) encapsulents.
The two products thus belong to the group of normal refractive index (NRI) encapsulants. They effectively protect the sensitive LED semiconductor chip against environmental influences. They can additionally serve as carriers for luminescent dyes, which can selectively influence the color of the light emitted by the LED and under normal room temperature. The LED encapsulents can protect the sensitive LED chip from environmental impact, and the phosphor carrier can effectively change the LED light beam color.
Taiwanese researchers develop new material to extend LED lifetime
Recently Taiwanese researchers developed a new type of thermal dissipation material to replace hard and thick aluminum thermal heat sinks. The research team claims it used polyamide and reduced graphene oxide (rGO) for the heat sink. The LEDs can more effectively disseminate heat internally from the LED lamp.
Meanwhile, the research and development team (R&D) developed a plastic material that has thermal properties similar to expensive graphene. The material can be molded into plastic, and it is easy to control the production. The material is capable of lowering equipment costs, weight, while producing flexible LED thermal dissipation material that significantly boosted LED lifetime.
New breakthroughs in LED thermal dissipation devices
Recently, China Light Industry senior engineer Kuanan Li introduced an innovative LED thermal dissipation technology that possesses independent intellectual property rights, which the company aims to solve key issues and points. The companies were able to successfully remove all obstacles and use a linear designed fan to forcefully dissipate heat and achieve good thermal dissipation effects. The inventor, Yixing Zhang noted the design solved thermal dissipation issues, and met LED drivers power demands of being highly efficient, highly reliable and low costs. The company founder noted this basically solved two major issues in LED development.
Wenzhou University College of Chemistry and Materials Engineering invents new material to extend white LED lifetime
LED lamps lifetime have been extended by nearly 10 years through innovative materials developed by Weidong Xiang, Assistant Professor at Oujiang College, Wenzhou University College of Chemistry and Materials Engineering. Elongated periods of illumination allows this material to be more widely applied in luxury automobiles, high speed rail, airplanes, subway and other lighting applications.
Xiang spent many years developing a yellow light on a single LED die chip that can be synthesized under high temperatures of 2,000℃. If a blue light LED chip is paired with a 24W light source on a 5.5 mm x 5.5 mm on a single die chip, the yellow die material can steadily emit white light. Due to the chips thermal resistance, high conductivity, LED lamps will become more resilient, and have longer lifetimes. The LED bulbs are not easily damaged by high temperatures after long hours of illumination, so it is highly suitable for lighting applications in luxury cars, automotive lights, high speed rail, airplanes and submarines.