Reversible Phase Transition, Switchable Second‐Order Nonlinear Optical and Dielectric Properties in a Bismuth(III)‐Based Compound: (R)‐3‐(Fluoropyrrolidinium) 2 BiBr 5

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

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 SbCl5 (1; 3FP=3-fluoropyrrolidinium) and (R-3FP)2 SbBr5 (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.

Two-step nonlinear optical switch in a hydrogen-bonded perovskite-type crystal

Switchable nonlinear optical (NLO) materials have aroused broad interest on account of their captivating optical and electronic properties. We demonstrate a novel perovskite-type crystal with exceptional hydrogen bond interactions that are associated with the onset of reorientational motions of organic cations and thus induce the occurrence of two successive phase transitions to be a two-step NLO switch. This finding affords an alternative approach for the design and assembly of switchable NLO materials.