Carrier transport mechanism in two-dimensional perovskite quantum well materials revealed by Dalian Institute of Chemical Technology

[ Instrument network instrument research and development ] Two-dimensional (2D) organic-inorganic hybrid perovskite semiconductor quantum well material is formed by inserting long-chain organic halogenated amine ligands in the three-dimensional (3D) perovskite lattice. 2D perovskite has unique properties such as flexible structure, large exciton binding energy, easily tuned band gap, and significantly improved moisture resistance, and has attracted wide attention in the fields of optoelectronic and quantum device applications. Previous studies generally believed that the carriers in 2D perovskites exist in the form of excitons, which are limited by the lifetime and mobility of excitons. The exciton migration distance is only a few hundred nanometers, which is more than an order of magnitude smaller than that of 3D perovskite materials. . Based on the carrier transport characteristics reported in the literature, 2D perovskite may not be comparable to 3D perovskite and other traditional semiconductor quantum well materials in terms of long-distance carrier transport device applications.

Recently, Jin Shengye’s team, a researcher in the Ultrafast Time-Resolved Spectroscopy and Dynamics Research Group of Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has made progress in the research of carrier dynamics in two-dimensional perovskite quantum well materials and found that it has broken the exciton migration limit The phenomenon of long-distance carrier transport.

The team used the established new method of dynamic visualization to observe for the first time the long-distance carrier transport phenomenon in the 2D perovskite single crystal PEA2MAn-1PbnI3n+1 (n=2~4) that breaks the exciton migration limit, and its migration distance It can reach 2~5μm. Using confocal fixed-point excitation of 2D perovskite single crystals, the low-energy state "boundary state" emission at a certain distance from the excitation point was observed through fluorescence scanning dynamic imaging, and the boundary state luminescence dynamics has obvious distance dependence. Based on experiments such as temperature, a new mechanism of defect state-assisted long-distance carrier transport is proposed. It is believed that this long-distance carrier transport is formed by defect-assisted exciton dissociation to form long-lived and non-luminous electron holes. Realized in a separated state. Through kinetic model fitting, the kinetic parameters of carrier migration in 2D perovskite single crystals with different layers (n values) are obtained. This unique property makes 2D perovskites comparable to 3D perovskites and other traditional semiconductors in terms of carrier transport performance. The results of the study have changed the perception of short carrier transport distances in two-dimensional materials, showing that It has application prospects in the field of high-efficiency energy/charge transport.

Relevant results were published in the Journal of the American Chemical Society. The research was supported by the National Natural Science Foundation of China, the National Key Research and Development Program, the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and the Chinese Academy of Sciences' Strategic Leading Science and Technology Special Project.