Elucidating Phase Transitions and the Genesis of Broadband Emission in MA1–xFAxPbBr3 Perovskites

The octahedral distortion plays a pivotal role in influencing various unique electrical and optical properties of organic lead halide perovskites (OLHPs). Unveiling the nature of the response of the local inorganic octahedra to the photophysical properties is a critical step toward understanding the formation of excited-state defects. Here, we report a fundamental understanding of the process of octahedral distortion and its variation with temperature in MA1–xFAxPbBr3 (x = 0, 0.5, 1) perovskites. Further, the origin of trap states which are responsible for the broadband emission has been elucidated with the help of detailed structural and photophysical analysis. We find that the intensity and Stoke shift of the broadband emission peaks and charge carrier dynamics are significantly influenced by the changes in Pb–Br bond lengths and Pb–Br–Pb angles. Our findings highlight the relationship between the octahedral distortion and the formation of trap states and provide further insights into tailoring the broadband emission by regulating the local inorganic octahedra in OLHPs.