Chirality-Induced Spin Optimization in Lead-Free Metal-Halide Hybrids for High-Performance Flexible X-Ray Detectors

Lead-free metal-halide hybrid x-ray detectors are fundamentally limited by strong exciton localization and inefficient carrier transport, preventing their deployment in high-sensitivity flexible imaging systems. Here we establish a chirality-modulated spin-engineering strategy that intrinsically overcomes these limitations by quantitatively linking molecular chirality, Rashba spin splitting, carrier transport, and detector performance in a chiral Bi/Sb metal-halide hybrid series, (S_1-rR_r-CHEA)₄(Bi_0.5Sb_0.5)₂I₁₀ (CHEA = 1-cyclohexylethylamine), where the enantiomeric ratio functions as a continuous structural control parameter. Homochiral assemblies maximize inversion-symmetry breaking, producing a giant Rashba coefficient up to 0.41 eV Å^-1 and enabling long-lived (> 1 ns) spin polarization that suppresses excitonic localization. As a result, the exciton binding energy decreases by 42% while the carrier mobility-lifetime product (μτ) increases fourfold, establishing an intrinsic spin-modulated transport mechanism in lead-free metal-halide hybrids. Flexible detectors fabricated from the optimized homochiral composition exhibit deformation-invariant x-ray imaging with a record sensitivity of 8002 µC Gy^-1 cm^-2, an ultralow detection limit of 75 nGy s^-1, and exceptional robust endurance under couples of stresses including thermal, humidity, mechanical, and irradiation. This work identifies molecular chirality as a programmable handle to control spin-orbit interactions and carrier dynamics, providing a general materials-level strategy for high-performance, environmentally benign radiation detectors and spin-enabled optoelectronics.