At present, China is in an important period of industrial restructuring and transformation of economic growth mode. It has become the consensus of LED industry to rely on technological innovation to promote industrial development.
LED industry has also achieved rapid growth under the joint promotion of policies, technologies and markets, and the industrial scale is growing day by day.
Looking back to 2018, LED lighting industry has made breakthroughs in many technologies.
Now, OFweek semiconductor lighting network editor has made a comprehensive inventory of some LED related new technologies and new application information around the world. We hope that you can learn from the application of creative nutrients, so as to create more excellent products.
Study on infrared broad spectrum light source array
Recently, Semiconductor Today, an international journal of Semiconductor industry, reported on the latest achievements of zhang ziyang's team from suzhou institute of nanotechnology and nanobionics of the Chinese academy of sciences.
The findings are published in Optics Letters.
The medium infrared broad spectrum light source is based on semiconductor quantum cascade material. The active layer of the light source consists of 30 repeated cascade periods separated by low-doped n-type InGaAs.
The active energy band structure designed by the researchers is shown in figure 1. It adopts a double-phonon resonance structure, and a periodic active region contains four coupled strain compensation In0.
The as / 322 In0.
635As quantum well.
This structure can achieve more efficient pumping of low level carriers by means of two optical phonon assisted relaxation, thus increasing particle number inversion and increasing spontaneous radiation efficiency.
The wide spectrum light source with this material structure has the advantages of lower threshold current density and higher output power.
Figure 1: quantum cascade band structure based on four-well coupled two-phonon resonance
"(source: Semiconductor Today)
In order to obtain the low reflectance (less than 10-6) required by restraining exciter to achieve superradiant luminescence, the device size of wide-spectrum light source in mid-infrared is generally large, so it is difficult to prepare an integrated device array structure.
The waveguide structure of the wide-spectrum light source device designed by the researchers is shown in figure 2, which is a two-channel ridged segmented waveguide device structure, consisting of straight end, inclined strip region and j-type waveguide.
The waveguide structure can meet the requirement of low reflectivity by the mutation of two reflectivity and the smaller device size.
Based on this structure, the researchers prepared a series of wide-spectrum light source arrays and obtained the continuous output power of 2 at room temperature.
4 mw, spectral width 199 cm - 1, far-field divergence Angle of 20 °.
Medium infrared light source has important applications in the fields of atmospheric communication, space remote sensing, chemical detection and medical diagnosis.
The work is supported by the national key research and development program and the natural science foundation of China.
Figure 2: schematic diagram of device array of mid-infrared quantum cascade wide-spectrum light source
Upper left: micrograph upper right: SEM image
Organic led research
Professor li feng's team from the school of chemistry, jilin university and the state key laboratory of supramolecular structure and materials prepared organic light-emitting diodes using organic light-emitting free radical materials, achieving nearly 100% quantum efficiency and solving the problem of low luminous efficiency of traditional fluorescent light-emitting materials.
The results were published in nature with jilin university as the first completion unit.
Light-emitting diodes (oleds) are the key components in the field of display and lighting. Compared with traditional light-emitting diodes (leds), organic light-emitting diodes (oleds) have the advantages of high contrast, ultra-thin and flexible, and have great market value and application prospect in the field of display and lighting.
In theory, only 25% of the energy of traditional organic light-emitting diodes (oleds) can be used for luminescence when they are powered on. How to convert the rest of the energy into photon luminescence has been a hot and difficult issue in this field for nearly 30 years.
The team found that organic light-emitting free radical materials with unique single-electron structure only produce bilinear excitons when electrified. Theoretically, 100% of bilinear excitons can be used for luminescence.
Organic light-emitting diodes (oleds) made from organic light-emitting free radical materials can solve the problem of low luminous efficiency of traditional oleds.
By continuously improving the material and device structure, the team developed free radical luminous materials and devices with high luminous efficiency.
Currently, the light-emitting materials used in organic light-emitting diodes are usually fluorescence and phosphor materials, but the former has limited luminous efficiency and the latter requires heavy metals with scarce resources, resulting in higher costs, li said.
In contrast, organic free radical materials are cheap organic compounds, which reduce the cost while maximizing the efficiency of electro-optical conversion.
The research was supported by the national natural science foundation of China, the ministry of science and technology's key research and development programs and the 973 program, the visiting scholar program of China scholarship council and the peiying project of jilin university.
According to foreign media reports, researchers have developed a new LED based on perovskite semiconductor, which has set a new efficiency record and is comparable to the best organic LED (OLED).
Perovskite LED with higher efficiency and lower cost is available
The perovskite-based LED, developed by researchers at Cambridge university, costs less to make than OLED, which is widely used in high-end consumer electronics, and can be adjusted to emit light through visible light and near-infrared spectra with high color purity.
The perovskite layer in the LED was designed to achieve nearly 100% internal luminous efficiency, opening up its future application prospects in display, lighting and communication as well as the next generation of solar cells.
These perovskite materials, like those used to make efficient solar cells, could one day replace commercial silicon solar cells.
Although perovskite-based leds have been developed, they are not as effective at converting electrical energy into light as traditional oleds.
Dr Dawei Di, of the cavendish laboratory at the university of Cambridge, said: "this perovskite-polymer structure effectively eliminates non-luminescence losses and is the first time that this performance has been achieved in a perovskite-based device.
With this hybrid structure, we can basically prevent electrons and positive charges from recombining through defects in the perovskite structure.
The perovskite-polymer blend used for the LED device, known as a body heterostructure, is made of two-dimensional and three-dimensional perovskite components and insulating polymers.
When ultrafast lasers hit such polymer structures, pairs of energy-carrying charge pairs move from the 2-d region to the 3-d region at trillionths of a second: much faster than the early layered perovskite structures used in leds.
The separated charges in the 3-d region then recombine and emit very strong light.
"Because the energy transfer from the 2-d region to the 3-d region occurs so quickly, and because the charge in the 3-d region is isolated from defects in the polymer, these mechanisms can produce defects that effectively prevent energy loss," Di said.
Baodan Zhao, lead author of the paper, said: "at the current density associated with display applications, the optimal external quantum efficiency of these devices is more than 20 per cent, creating a new record for perovskite leds and similar to the efficiency of the best OLED currently on the market."
While these perovskite-based leds can rival oleds in efficiency, they still need better stability if they are to be widely used in consumer electronics.
First developed perovskite leds have a lifespan of only a few seconds.
However, the LED developed by the current research and development has a half-life of nearly 50 hours, which is a huge progress for the improvement achieved in just four years, but it still does not reach the life required for commercial applications, so extensive industrial development planning will be required.
"Understanding the degradation mechanism of the LED is a key to continuous improvement in the future," Di said.