Halogen Engineered Chiral Amplification in Chiral Hybrid 2D Perovskites for Self‐Powered Circularly Polarized Light Detection

Chiral hybrid perovskites hold great promise for optoelectronic and spintronic applications due to their superior optoelectronic properties. However, the development of self‐powered circularly polarized light (CPL) detectors is often hindered by weak chiroptical anisotropy and inefficient zero‐bias operation. Herein, we report the synthesis of chiral ( R/S ‐3BrMBA) 2 PbBr x I 4‐x (0 ≤ x ≤ 4) hybrid perovskites, demonstrating that halogen engineering is an effective strategy for chiral amplification. Through this approach, the g CD value is enhanced by more than 5‐fold, attributed to intensified octahedral distortion and the concomitant modulation of spin–orbit coupling. Remarkably, we achieved a Zeeman splitting of 0.663 meV, a 2.4‐fold increase over the pristine sample, which represents the highest value reported to date for chiral 2D perovskites. Furthermore, the (R‐3BrMBA) 2 PbBr 2 I 2 device exhibits an open‐circuit voltage exceeding 5 V, breaking the traditional bandgap limit while enabling self‐powered operation with a g Iph of 0.24. This work confirms halogen engineering as a robust strategy for chirality amplification, paving the way for advanced self‐driven chiral photodetectors.