Introduction
Recently, a team led by Professor Liu Chuan and Associate Professor Liu Baiquan from the School of Electronics and Information Engineering (Microelectronics) at Sun Yat-sen University has achieved significant breakthroughs in the field of light-emitting diodes (LEDs). Utilizing core/shell colloidal quantum well technology, they have precisely controlled exciton dynamics, effectively reducing exciton recombination defects, balancing charge injection, and suppressing energy transfer between colloidal quantum wells. This innovative approach not only significantly enhances the efficiency of LED devices but also successfully integrates them with thin-film transistors and circuit boards, realizing active addressing and a “pipeline” effect for displays.
Advantages of Colloidal Quantum Well LEDs
Colloidal quantum well LEDs, a new type of nanocrystal LED, show great potential in display applications due to their high color purity, narrow half-width electroluminescent performance, and compatibility with solution processing. The team explored the impact of different shell thicknesses in core/shell heterostructured colloidal quantum wells on exciton dynamics, revealing a strong dependency between exciton generation and shell thickness.
Key Findings
The research indicated that increasing the shell thickness within a certain range significantly enhances radiative recombination efficiency while reducing Auger recombination, thereby vastly improving the overall performance of colloidal quantum well LEDs. This advancement led to devices exhibiting high efficiency, high brightness, and ultra-low efficiency roll-off, with external quantum efficiency reaching 13.43%, current efficiency at 9.20 cd/A, and power efficiency at 6.04 lm/W.
These metrics represent the highest levels currently reported for red light in the two-dimensional nanocrystal LED range (600-700 nm). Furthermore, during the transition from a brightness of 1,000 cd/m² to 10,000 cd/m², the external quantum efficiency only slightly decreased from 13.15% to 12%, marking the best performance among reported colloidal quantum well LEDs.
Integration with Flexible Substrates
By integrating with PEN flexible substrates, the team further realized flexible colloidal quantum well LEDs, achieving an external quantum efficiency 40 times greater than previously reported best flexible colloidal quantum well LEDs. Utilizing a high-current TFT driving circuit, the research team successfully demonstrated the on/off control of single or multiple colloidal quantum well LEDs, achieving active addressing and the “pipeline” display effect. This accomplishment not only paves the way for further research and applications of colloidal quantum well LEDs but also offers new insights and strategies for the future of display and lighting technologies.
Publication and Acknowledgments
The research findings were published in the internationally renowned academic journal Applied Physics Reviews, titled “Exciton control enables high-performance colloidal quantum well light-emitting diodes,” and was selected as a Featured Article. The first unit of the paper is the School of Electronics and Information Engineering (Microelectronics) at Sun Yat-sen University, with doctoral students Hu Sujuan from Sun Yat-sen University and Xiang Wenbin from Southeast University as co-first authors. Associate Professor Liu Baiquan and Professor Liu Chuan from Sun Yat-sen University are co-corresponding authors, with other collaborators from Southeast University, Nanyang Technological University, South China University of Technology, and Hong Kong University of Science and Technology. This research was funded by the National Natural Science Foundation (62104265) and the Guangdong Province Science and Technology Program (2022A0505020022, 2021A0505110009).
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