Shandong University has made new progress in near-infrared luminescent materials and LED research

Recently, the team of Professor Wang Liang of Shandong University has made important progress in the research of near-infrared luminescent materials and light-emitting diodes. The relevant results were published in the journal Advanced Materials (impact factor: 26.8).

Near-infrared light-emitting diodes are crucial in the fields of night vision, biomedical imaging, optical communications, sensing and security. Metal halide luminescent materials have become core candidate materials due to their narrow half-peak width, adjustable band gap, high carrier mobility and other advantages. However, there are key bottlenecks in this field: First, near-infrared phosphors have long focused on improving the internal quantum efficiency (IQE), neglecting the absorption efficiency (AE), resulting in stagnant external quantum efficiency (EQE); second, it is difficult to achieve efficient thermal evaporation of Yb-doped CsPbCl3 near-infrared light-emitting diodes with wavelengths exceeding 950 nanometers, and the existing defect-assisted energy transfer mechanism is single. In response to these problems, Professor Wang Liang's team proposed innovative solutions, laying the foundation for performance breakthroughs and application expansion of near-infrared light-emitting diode devices.



EQE for near-infrared luminescence To solve the stagnation problem, the team of Professors Wang Liang and Yu Weiyang, together with the team of Professor Zheng Chuantao of Jilin University and Professor Xiao Zewen of Central South University, proposed a new strategy to collaboratively optimize AE and IQE, and designed a lead-free perovskite single-component solid solution material Cs2Te0.92Mo0.08Cl6. The material achieves broadband near-infrared emission from 750 to 1350 nanometers, with an internal quantum efficiency of 97.4%, and a record external quantum efficiency of 65.6% among broadband near-infrared phosphors over 900 nanometers; its excellent performance comes from the synergistic effects of strong photon capture, low phonon energy and I-type energy band alignment.

In addition, the material has excellent stability. The near-infrared LED prepared based on the 395-nanometer UV chip has an electro-optical conversion efficiency of 15.2% and a light output power of 112 mW. It has proven its practical application value in the fields of ethanol concentration detection, solar energy collection, night vision and anti-counterfeiting. Related work is titled “Unlocking High External Quantum Yield for Broadband Near-I nfrared Emission From Lead-Free Perovskite Variant Solid Solutions Cs2Te1‒xMoxCl6" was published in Advanced Materials. Postdoctoral fellow Li Xin of Shandong University is the first author of the paper, Professor Wang Liang is the core corresponding author, and Shandong University is the first author unit and core research unit.

In addition, in the preparation of electroluminescent near-infrared light-emitting diodes through thermal evaporation with heterogeneous integration and angstrom-level thickness control, the traditional CsPbCl3:Yb luminescence has a single defect-assisted energy transfer mechanism and lacks a coordinated path to accelerate visible light to near-infrared energy transfer. The team of Professors Wang Liang and Yu Weiyong proposed a localized engineering strategy for bound excitons through thermal evaporation of CsPbCl3:Yb with heterogeneous integration and angstrom-level thickness control. Locally bound excitons were constructed in the system, and experiments confirmed that they can significantly promote the energy transfer from the matrix to the Yb dopant. Combining atomic scale characterization and first principles calculations, the exciton transfer driven by bound excitons was analyzed. transfer mechanism and confirmed the key regulatory role of Cs vacancy defects.

The near-infrared light-emitting diode prepared based on this mechanism has an external quantum efficiency of 8.9% and a radiant brightness of 410 mW·Sr-1·m-2, setting a new record for near-infrared light-emitting diodes with wavelengths > 950 nm prepared by thermal evaporation. The related work was published in Advanced Materials under the title "Exciton Localization Engineering in Thermally Evaporated Yb-Doped CsPbCl3 Near-Infrared Light-Emitting Diodes". Wang Shuo, a master's student of Shandong University, is the first author of the paper, Professor Wang Liang is the core corresponding author, and Shandong University is the first author's unit and the only corresponding author's unit.

Wang Liang’s research group has been engaged in research on optoelectronic materials and functional optoelectronic devices for a long time. Currently, it has worked in Nature Energy, Natu Published research papers in academic journals such as re Communications, Science Advances, Advanced Materials (3 articles), Advanced Energy Materials, Advanced Functional Materials, etc. Relevant research work has been supported by projects such as the National Key Research and Development Program, the National Natural Science Foundation of China, the Shandong Province Taishan Scholars Fund, and the Shandong Province Natural Science Foundation. (Source: Shandong University)