Halogen Substitution as a "Chirality Editor" for Amplifying Spin-Selective Transport in Lead-Free Metal-Halide...

Lead-free metal-halide hybrids hold promise as flexible semiconductors for X-ray detection, but their application is constrained by inefficient carrier transport. Here, we introduce halogen substitution on chiral molecular cations as a "chirality editor" to modulate the chiral electrostatic environment and thereby amplify spin-selective transport in bismuth-based hybrids. A series of nine (S/rac/R-XPEA)₄Bi₂I₁₀ compounds, where X = F, Cl, or Br and XPEA = 1-(4-halophenyl)ethylamine, is systematically investigated, revealing that substitution from F to Br modulates molecular dipoles and local structural distortions, and enhances Rashba spin splitting. Consequently, chiroptical activity increases by nearly one order of magnitude and spin polarization efficiency rises from 68% to 89%, as confirmed by magnetoconductive atomic force microscopy. The amplified chiral-induced spin selectivity (CISS) effect yields a 3.4-fold enhancement in carrier mobility-lifetime product (μτ up to 3.26 × 10^-3 cm² V^-1) while simultaneously reducing dark-current drift by threefold. The optimized Br-substituted homochiral flexible X-ray detector achieves a sensitivity of 8865.82 ± 403 µC Gy^-1 cm^-2 and an ultralow detection limit of 7.16 nGy s^-1. Overall, this work establishes a structure-property-performance framework that positions halogen-based "chirality editing" as an efficient strategy for high-performance radiation detectors.