The world's top Ten innovative LED light source devices in 2020 (4/6)
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Author : Shenzhen Crown Lighting
Update time : 2021-06-28 21:26:05
Display and interpretation of the world's top ten innovative LED light source devices in 2020 (4/6)
6. High-performance red light QLED
In November, the Changchun Institute of Applied Chemistry of the Chinese Academy of Sciences and the Ding Junqiao team of Yunnan University used an organic electron transport layer to replace the traditional ZnO inorganic electron transport layer and successfully assembled a high-performance red quantum dot light-emitting diode (QLED).
In the process of device development, the research team selected nitrogen-containing heterocyclic compounds as the organic electron transport layer, and at the same time fine-tuned the molecular structure of the central core through energy band engineering. When the central nucleus changes from benzene ring to pyrimidine and triazine, the lowest unoccupied molecular orbital (LUMO) energy level increases from -2.28 eV to -2.79 eV and -3.07 eV, and the electron injection ability gradually increases. Finally, the organic electron transport layer TmPPPyTz with triazine as the central core achieves the optimal carrier balance, and the external quantum efficiency (EQE) of the device is as high as 13.4% (18.8 cd/A, 23.9 lm/ W), the CIE color coordinate is (0.68, 0.32).
The successful preparation of the QLED device will bring important application value to the improvement of the optical quality of lighting and display products.
7. High-efficiency InGaN-based orange-red LED
In the same month, the research group of Academician Jiang Fengyi of Nanchang University in China developed the latest high-efficiency InGaN-based orange-red LED.
(a) Schematic diagram of the high-efficiency orange LED epitaxial material structure and
(b) its cross-sectional TEM test results
During the development of the LED device, the research team introduced the alternate growth method of indium gallium nitride red light quantum well and yellow light quantum well based on the silicon substrate gallium nitride technology, and combined with the V-shaped pit technology, which greatly alleviated the high Indium in the red light quantum well. The problem of component segregation, and then based on the V-shaped pn junction and quantum well band gap engineering, the radiation recombination rate in the red light quantum well has been greatly increased, so that the prepared InGaN-based orange-red light LEDs emit light at 594, 608, and 621 respectively. At nm, the power conversion efficiencies are 30.1%, 24.0%, and 16.8%, respectively. Compared with the previous InGaN-based LEDs in the same band, the light efficiency is increased by about ten times.
The successful development of this LED device proves that InGaN materials will have great potential and bright application prospects in the production of red light pixel chips for display applications.
