LED quantum dot light-emitting diode research progress

Recently, with the support of the National Natural Science Foundation of China, the Peng Xiaogang Group of Chemistry Department of Zhejiang University and the Jin Yizheng Group of Materials Department have made important progress in the field of quantum dot light-emitting diode research. Related research results were published in Nature. This paper reports a new type of LED device using quantum dots as electroluminescent materials. Its performance far exceeds other quantum dot LEDs reported in the current literature, and the new device can be prepared by a simple solution processing route.

LED has been recognized as the core device for next-generation lighting and display. Gan epitaxially grown quantum well LED devices are currently popular products on the market. However, the Gan epitaxial growth quantum well requires ultra-high vacuum, ultra-high purity raw materials, ultra-density electrical energy consumption and the like. To this end, both the display industry and the lighting industry have chosen a relatively low-cost idea of ​​combining blue LEDs with down-converted rare earth phosphors. However, this combination of routes leads to defects such as low light quality and incomplete color gamut.

Unlike the Gan quantum well LED, the luminescent center of the OLED device is an organic molecule and can be prepared under less demanding vacuum conditions. Organic light-emitting diodes have been used in small-screen displays, but their thermal stability and chemical stability have always been a thorny problem, which is directly manifested by the harsh processing requirements of the device and the insufficiency of device lifetime.

Obviously, quantum dot light-emitting diodes are expected to combine the advantages of both Gan quantum well LEDs and organic light-emitting diodes. However, after 20 years of unremitting efforts by scientists, the comprehensive performance of quantum dot LEDs – including efficiency, longevity, and processing – is far behind expectations. This is mainly due to the compatibility of quantum dots with quantum dot light-emitting diode devices and the special structure of quantum dot light-emitting diodes.

The team of Zhejiang University designed and synthesized special quantum dots for quantum dot light-emitting diodes, and analyzed the device characteristics of quantum dot light-emitting diodes. The key problems of the device structure were found, and a layer of nano-insertion was inserted into the device. The insulating layer solves the key difficulty of positive and load carrier injection balance. The success of these two aspects has experimentally verified the feasibility of the practical application of quantum dot light-emitting diodes. This indicates that quantum dot LEDs are expected to play an important role in both lighting and display industries.