Pressures Tuning the Band Gap of Organic-Inorganic Trihalide Perovskites (MAPbBr3): A First-Principles Study.

Organic-inorganic trihalide perovskites have become one of hotspots in the field of photoelectric functional materials. Based on first-principles calculations within density functional theory, we analyzed the changes of the electronic structure of the perovskite MAPbBr₃ under different pressures. We found that the band gap of compressed perovskite MAPbBr₃ exhibits a significant red-shift under a relatively mild pressure of ∼ 1.877 GPa and becomes larger under higher pressure. This can be semiquantitatively explained by the effects of hydrogen bonding between organic MA cation and bromine framework. These effects drive rotations of PbBr₆ octahedral in order to fit the local environment. Results of Bader analysis under different pressures suggest that Coulomb interaction driven by charge transfer leads to movement of the amine end of MA cation towards Br atoms and alters the predominant Pb-Br-Pb bond angle. Given that, compressed perovskite MAPbBr₃ exhibits notable band gap changes. Our results provide an efficient and clean approach to optimize photovoltaic properties of organic-inorganic trihalide perovskites. [ABSTRACT FROM AUTHOR]