Highly Effective Hybrid Copper(I) Iodide Cluster Emitter with Negative Thermal Quenched Phosphorescence for X‐Ray Imaging

The low efficiency triplet emission of hybrid copper(I) iodide clusters is a critical obstacle to their further practical optoelectronic application. Herein, we present an efficient hybrid copper(I) iodide cluster emitter (DBA)4Cu4I4, where the cooperation of excited state structure reorganization and the metallophilicity interaction enables ultra‐bright triplet yellow‐orange emission with a photoluminescence quantum yield over 94.9 %, and the phonon‐assisted de‐trapping process of exciton induces the negative thermal quenching effect at 80–300 K. We also investigate the potential of this emitter for X‐ray imaging. The (DBA)4Cu4I4 wafer demonstrates a light yield higher than 104 photons MeV−1 and a high spatial resolution of ≈5.0 lp mm−1, showing great potential in practical X‐ray imaging applications. Our new copper(I) iodide cluster emitter can serve as a model for investigating the thermodynamic mechanism of photoluminescence in hybrid copper(I) halide phosphorescence materials. The new hybrid copper(I) iodide cluster (DBA)4Cu4I4 enables ultra‐bright triplet yellow‐orange emission with a PLQY>94.9 % by the coaction of excited state structure reorganization and the metallophilicity interaction, and the phonon‐assisted de‐trapping process of exciton induces the negative thermal quenching effect at 80–300 K. Our investigation shows that this material has a great potential in practical X‐ray imaging applications.