Halogen Substitution Regulates High Temperature Dielectric Switch in Lead‐Free Chiral Hybrid Perovskites

Abstract Hybrid metal halides (HMHs) based phase transition materials have received widespread attention due to their excellent performance and potential applications in energy harvesting, optoelectronics, ferroics, and actuators. Nevertheless, effectively regulating the properties of phase transitions is still a thorny problem. In this work, two chiral lead‐free HMHs ( R ‐3FP) 2 SbCl 5 ( 1 ; 3FP=3‐fluoropyrrolidinium) and ( R ‐3FP) 2 SbBr 5 ( 2 ) were synthesized. By replacing the halide ions in the inorganic skeleton, the phase transition temperature of 2 changes with an increase of about 20 K, compared with 1 . Meanwhile, both compounds display reversible dielectric switching properties. Through crystal structure analysis and Hirshfeld surface analysis, their phase transitions are ascribed to the disorder of the cations and deformation of the inorganic chains.