Recently, Henan University cooperates with China University of Science and Technology and other units to make breakthrough progress in visible light quantum sub-lighting diodes (QLEDs). This work develops a new nuclear shell structure quantum dot, which has developed high-brightness, high efficiency and long life red green blue three-primary QLLD devices, including multiple performance indicators to record world records, including red and green brightness (356 , 000 Cd / m2 and 614,000 Cd / m2) and efficiency (21.6% and 22.9%), blue brightness (62,600 CD / m2) and green and blue devices (1.7 × 106 h, respectively) And 7000 h). The study is expected to accelerate the process of advancing QLEDs in highlighting and efficient display and lighting applications.
Breakthrough in the Gas Galasm-based high-brightness Blu-ray LED in the 1990s, opened the new era of LED lighting and display (three Japanese scientists have contributed to the 2014 Nobel Physics Award). The QLED based on the semiconductor quantum dots, due to better monochrome, color saturation and lower preparation costs, exhibiting broad application prospects in the field of display and lighting. After nearly a few years, the main performance indicators such as luminous brightness, external sub-efficiency (EQE) and life have been greatly improved. However, in the previous work, the device is too low in high brightness, and the brightness is too low in high efficiency. How to make the device maintain high efficiency while maintaining long life and high stability, is a problem that is urgent to solve in the QLED field, and is also a key technical bottleneck that restricts its application in the field of display and lighting.
The main reason for causing the above-mentioned "fish and bear's paw" is that the quantum price of quantum dots in the QLED light-emitting layer is generally deep, and the hole transport layer does not match, causing the hole injection efficiency, and electronically injection unbalanced. In response to this problem, the research team starts from the design of the light-emitting layer quantum dots, based on the "low temperature nucleation, high temperature long shell", the CDSE / Znse new core of the fluorescence quantum yield and strong stability is synthesized. Structure quantum dots (Fig. 1). Such high-quality nuclear housing structural quantum points act as a light-emitting layer, which can improve the matching of the transmission layer level, effectively reduce the hole injection barrier, improve the injection efficiency of the carrier, and overcome the incorporation of hole injection due to hole injection, electronics A series of problems caused by excessive injection, thereby greatly enhances the overall performance of the device.
Figure 1 CDSE / ZNSE Nuclear Shell Structure Quantum Point Ball Electron Mirror and Element Distribution
Based on this new structural system, the research team has achieved the highest brightness and external quantum efficiency of the red green blue QLED device, which reached 356,000 CD / M2, 614,000 CD / M2, 62, 600 CD / M2 and 21.6, respectively. %, 22.9%, 8.05%, its red, green two-color brightness and efficiency, and blue brightness are currently the highest record (Figure 2). The work broke through the low-efficiency, high-efficiency low-brightness, high-efficiency, high-efficiency, high-efficiency, and high-brightness, high-efficiency, high-efficiency, high-increasing, high-increasing, high-increasing, high-increasing, high-increasing, high-increasing, high-efficiency, high-efficiency, high-efficiency, high-efficiency, high-efficiency, broccoli QLED device.
Figure 2 Red Green Blue Sany Color QLED Device Performance
In order to more accurately describe the light-emitting characteristics of the new QLED, the research team introduced a new concept-"Effective Brightness (EFL), defined as the product of peak EQE and its relative luminous intensity. Figure 3 is a comparison of the EFL of the three-color QLED of this work. It can be seen that the EFL of the green device has doubled, and the two colors of red blue have a near level. Moreover, from the light of the lighting of brightness and efficiency, the three-color QLEDs obtained by this work have exceed the corresponding threshold.
Figure 3 Red Green Blue SanyQLLED "Effective Brightness" (EFL) and Existing Work Comparison
The stability of the device (life) is another key factor to restrict its application. The new QLED device developed by this work also performs exceptional life, red and green QLED devices have a life of 1.6 × 106 h, and the life of blue has reached 7000 h. The life of green and blue devices is also the most world. Long record.
These research results and the established device model not only demonstrate QLEDs in highlighting the possibility of highlighting the application of lighting, but also provides new ideas for future QLED material system design and device structural optimization.
Related research results
Visible Quantum Dot Light-
Emitting Diodes with Simultaneous High Brightness AndEffic Ince Posted in Nature Photonics [2019, 13, 192-197]. Professor Shen Huibin, Henan University, is the first author of the paper, Professor Du Zawa, Henan University, Professor Li Linong and Professor Zhang Zhenyu, China University of Science and Technology, as a joint communication author.
This work has been funded by the Ministry of Natural Science Foundation and the Ministry of Science and Technology.
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