Photoinduced Structural Relaxation in Chiral Copper(l) Iodide Cluster Scintillators for Circularly Polarized Radioluminescence Imaging

ABSTRACT Circularly polarized luminescence offers untapped potential for enhancing x‐ray imaging resolution by suppressing optical crosstalk, yet its integration into high‐performance scintillators remains unexplored. Here we report a new class of chiral copper(I) halide scintillators, including enantiopure R‑/S‑3‑MLCuI (3‐ML represents 3‐methylmorpholine) circularly polarized scintillators and racemic Rac‑3‑MLCuI scintillators. Strategic enantiomer selection enables precise control over crystal symmetry—chiral P4 2 2 1 2 vs. centrosymmetric C2/c—dictating chiroptical activity. Combining TD‐DFT, in situ XAS, and ultrafast spectroscopy, we elucidate that emission originates from cluster‐centered self‐trapped excitons confined within discrete [Cu 4 I 4 ] cores, where pronounced excited‐state Cu─Cu contraction and Cu─I elongation induce strong exciton‐phonon coupling. Homochiral ligand environments impart persistent chiral imprinting, yielding |g lum | values up to 1.0 × 10 −2 . The materials exhibit record light yields (58 000 photons•MeV −1 ), exceptional x‐ray stability (>99% retention after 115 Gy), and ultra‐low detection limits (78.9 n Gy air •s −1 ). A flexible S‐3‐MLCuI@TPU film incorporating polarization‐gated imaging achieves 21.2 lp/mm resolution—significantly surpassing conventional scintillators by suppressing optical crosstalk. High‑fidelity x‑ray imaging of complex biological and electronic structures is demonstrated. This work provides a structure–property relationship that enables circularly polarized scintillation in chiral copper–iodide clusters, offering insights for further development of related systems.