What are the structural and optical changes in MAPbBr3 single crystals due to the halide exchange reaction with methyl iodide?

Label:chem

Topic
The halide exchange reaction involving methyl iodide as a source of iodide ions can induce significant structural and optical changes in MAPbBr3 single crystals. These changes are crucial for tailoring the optoelectronic properties of perovskites for various applications.

From: "Tuning emission and bandgap dynamics of MAPbBr₃ single crystals through halide exchange with methyl iodide", Chemical Physics Impact, Volume 10, June 2025, 100807
Answer
The halide exchange reaction with methyl iodide induces significant structural and optical changes in MAPbBr3 single crystals. Structurally, the initial MAPbBr3 crystals exhibit a cubic crystal structure with a space group of m3m and a lattice constant of 5.940 Å. As iodide ions from methyl iodide replace bromide ions, the crystal structure evolves into a mixed halide perovskite, MAPb(Br/I)3. Optically, the bandgap decreases from 2.26 eV to 1.7 eV, and the emission spectrum shifts from green (540 nm) to red (730 nm). Elemental analysis shows a change in the atomic molar ratio of bromine to lead from approximately 3:1 to a lower bromine content, indicating the successful incorporation of iodide ions. These changes highlight the dynamic nature of the halide exchange process and its direct impact on the material's optoelectronic properties, enabling precise control over the bandgap and emission characteristics for optimized performance in optoelectronic devices.
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