The research group led by Lu Xujie at the Beijing High Pressure Science Research Center (HPSTAR), in collaboration with Fu Yongping from Peking University and Jin Song from the University of Wisconsin-Madison in the United States, has delved into the synergistic regulation of the intra-layer and inter-layer structures in two-dimensional perovskites using high-pressure and chemical methods. They have investigated the impact of this regulation on excitonic properties and optoelectronic performance. The team has established a quantitative structure-performance relationship mathematical model for designing two-dimensional perovskite structures. Guided by this model, they have successfully synthesized high-performance two-dimensional perovskite materials. The related findings have recently been published in "Nature Communications."
Developing high-performance two-dimensional metal halide perovskite materials requires a deep understanding of the correlation between excitonic behavior and structure-performance. The chemical formula for two-dimensional metal halide perovskites is (LA)2(A)n-1PbnX3n+1. To achieve optimal excitonic properties in complex multi-layered systems (n≥2), both intra-layer and inter-layer structural parameters must be considered to construct materials with synergistically optimized intra-layer and inter-layer structures.
By introducing high-pressure structural regulation, the research team, using the example of two-dimensional perovskite (BA)2(GA)Pb2I7, achieved controllable modulation of excitonic properties. They transitioned the balance of carrier types from bound excitons to free excitons and free carriers, increasing the fluorescence intensity by 72 times at 2.1 GPa pressure. Further compression to 3.1 GPa resulted in a 10-fold enhancement in photoconductivity.
To more accurately quantify the impact of structural regulation on excitonic and optoelectronic performance, the research team proposed a new structural design model. Based on this model, they designed and synthesized a novel two-dimensional perovskite (CMA)2FAPb2I7 with synergistically optimized intra-layer and inter-layer structures. Compared to (BA)2(GA)Pb2I7, the new material exhibited a more symmetrical emission peak, with a 21-fold increase in fluorescence intensity and a fluorescence quantum yield of 59.3%, the highest efficiency among similar materials.
The established quantitative structure-performance relationship mathematical model for designing two-dimensional perovskite structures provides an important reference for the design and preparation of high-performance two-dimensional metal halide perovskite materials.
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