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All-inorganic perovskite quantum dots (CsPbX3, X = Cl, Br, I) have excellent optical and electrical properties and have shown great potential in photovoltaic devices such as solar cells, light emitting diodes, and lasers. However, similar to the organic-inorganic hybrid perovskite materials, the halogen-containing all-inorganic perovskite QDs are easily decomposed in contact with air due to the instability of their crystal structure in high temperature or humid environments, greatly limiting the The practical application of this material. For this reason, people have explored methods such as surface silica coating and surface chlorination to increase their stability, but these methods cannot fundamentally solve this problem. How to greatly improve the stability of all inorganic perovskite materials and regulate their photoelectric properties has become a research hotspot for many scientists at home and abroad.
Under the support of the National Natural Science Foundation of China, the Chinese Academy of Sciences’ Strategic Pilot Science and Technology Project, the “973†Program of the Ministry of Science and Technology, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the Hongmao Group Research Group and the Chen Xueyuan Research Group of the Institute of Material Structure of the Chinese Academy of Sciences jointly with Nanjing University of Science and Technology Professor Zeng Haibo's research group, Liu Yongsheng and other researchers proposed a simple and efficient Mn2+ substitution strategy to solve the problem of poor stability of all inorganic perovskite quantum dots from the perspective of stabilizing the lattice structure of CsPbX3 perovskite quantum dots. Through density functional theory first-principles calculations, the team found that when the bivalent matrix cation Pb2+ (~1.33 Å) in the CsPbX3 perovskite quantum dot lattice is replaced by a small amount of Mn2+ (~0.97Å) with a small ionic radius, The lattice will shrink due to Mn2+ doping. Since the Mn-X bond has a much higher dissociation energy than the Pb-X bond, the shrinkage of this lattice causes the formation energy (or binding energy) of the Mn2+ doped CsPbX3 quantum dots to be comparable to the pure quantum dots. Improvements have, to a certain extent, stabilized the crystal lattice of CsPbX3 perovskite quantum dots, which can significantly improve the thermal stability, air stability, and optoelectronic properties of perovskite QDs. Thanks to this, the research team also found that light-emitting diodes based on Mn2+ doped CsPbX3 QDs exhibit higher luminance, external quantum efficiency, and current efficiency than pure QDs, which fully demonstrates Mn2+ doping. The advantages of CsPbX3 quantum dots in building high-performance, long-term stable optoelectronic devices.
This work provides a new strategy for stabilizing CsPbX3 perovskite quantum dots, which will have an important impact on the optoelectronic applications of fully inorganic perovskite quantum dots. The above research results have recently been published in the full text of the "American Chemical Society", the first author of the paper is Zou Shengzheng, a doctoral student.
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