Strong Linear and Nonlinear Chiroptical Activity in 1D Chiral Bismuth‐Halide Perovskite

ABSTRACT Chiral metal halide perovskites have attracted considerable attention in both linear and nonlinear chiral optics, including circularly polarized photoluminescence (CPL) and chiral second harmonic generation (SHG). However, simultaneously achieving an excellent CPL and chiral‐SHG response with a single chiral perovskite crystal remains a significant challenge, particularly in low‐dimensional lead‐free chiral perovskites. In this work, 1D bismuth‐based chiral perovskites (R‐/S‐β‐MPA) 2 BiI 5 were successfully synthesized, exhibiting anomalous free exciton emission rather than self‐trapped exciton. This free exciton emission could avoid the spin relaxation process of the self‐trapped exciton emission, and thus make CPL with an average degree of circular polarization (DOCP) of 7.2% under linearly polarized excitation. More importantly, chiral perovskite (R‐β‐MPA) 2 BiI 5 presents bond length distortion of 3.2 × 10 − 2 and bond angle distortion of 35 deg 2 , which not only induces strong CPL, but also gives rise to chiral‐SHG response with a dissymmetry factor () up to 0.52. Our work provides a new approach for the realization of multifunctional chiroptical materials, which is promising in chiral‐optoelectronic applications.