Halogenated Chiral Spacer Integration in Silver Bismuth Double Perovskites for Efficient and Selective CPL Photodetection

Chiral double perovskites (DPs) have emerged as a versatile class of materials for detecting circularly polarized light (CPL), offering sustainable alternatives to toxic Pb-based systems. Despite their superior oxidative stability, the interplay between A-site chiral cations and B-site metal cations in DPs remains poorly understood, particularly regarding its influence on the electronic structure and chiroptical activity. In this study, we propose a rational chiral cation design strategy in which halogen substitution facilitates cooperative coupling with bond elongation induced by Jahn-Teller distortion in the inorganic layer, thereby revealing an enhanced chirality transfer phenomenon across the hybrid framework. Moreover, halogen···halogen interactions contribute to increased lattice rigidity in the 2D DPs, enhancing phase stability in thin-film configurations. As a result, a CPL photodetector based on Br-substituted chiral DPs achieves a CPL distinguishability of 0.32, the highest reported value among 2D chiral DP-based devices, alongside high photodetection performance and extended operational stability.