Highly Stable Chiral Hybrid Bismuth Halides With Giant Anisotropy for Self‐Driven Circularly Polarized Light Detection

Despite the great potential for chiral nonlinear optics and circularly polarized light (CPL) detection, the development of lead‐free chiral metal halides that simultaneously exhibit high environmental stability and large octahedral distortion remains a significant challenge. Herein, for the first time we report one‐dimensional, highly water‐tolerant, and chiral ( R/S )‐MPZBiBr 5 (MPZ = 2‐methylpiperazinium) bismuth halides. The short interchain spacing combined with strong hydrogen‐bonding interactions induces significant octahedral distortion. Owing to this substantial distortion, S ‐MPZBiBr 5 achieves a remarkably high second‐harmonic generation circular dichroism anisotropy factor ( g SHG‐CD ) of 0.61, along with an exceptional laser damage threshold of 37.68 GW·cm −2 . Furthermore, S ‐MPZBiBr 5 achieves a significant bulk photovoltaic effect through the combined action of local spontaneous polarization and non‐centrosymmetric structure. Thereby, S ‐MPZBiBr 5 demonstrates outstanding self‐driven CPL detection performance, delivering an anisotropic responsivity factor ( g res ) as high as 0.46 at 0 V bias. This work paves the way for designing high‐performance, lead‐free chiral metal halides for advanced applications in nonlinear optics and CPL photodetection.