Boosting Crystal Growth and Radioluminescence in Hybrid Cu(I) Halide Scintillators via Additive‐Strengthened Ionic and Electron–Phonon Interactions

Abstract We herein address two fundamental challenges in rod‐like ionic hybrid copper(I) halide scintillators—insufficient metal‐to‐ligand charge transfer leading to low radioluminescence efficiency, and anisotropic crystal growth that restricts the fabrication of large‐area single‐crystalline scintillator screen. Guided by computational insight, we introduce a “one stone, two birds” molecular strategy employing neutral 1,2‐propanediamine (1,2‐PDA) as a dual‐function additive in C 6 H 18 N 2 Cu 2 I 4 . Comprehensive mechanistic studies reveal that 1,2‐PDA not only strengthens ionic interactions between organic ligand (C 6 H 18 N 2 2+ ) and Cu(I) halide clusters, promoting oriented aggregation at crystal interfaces, but also induces significant lattice distortion upon defect incorporation, which enhances intersystem crossing and intensifies electron–phonon coupling, thereby boosting self‐trapped exciton (STE) emission. This synergistic mechanism yields a 3‐fold enhancement in photoluminescence quantum yield (PLQY: 17.53% to 52.96%) and a 2.77‐fold enhancement in radioluminescence intensity. Moreover, we achieved a large‐area single‐crystalline film (≈10 × 7 × 0.31 mm 3 ) demonstrates exceptional X‐ray imaging resolution of 22.3 lp mm −1 . This approach demonstrates broad applicability across diverse hybrid metal halides, concurrently improving crystal dimensionality and scintillation performance, thus establishing a versatile molecular design rule for high‐performance radiation detection materials.