Crown Ether‐Assisted Alkali‐Metal Copper(I) Iodide Supramolecular Scintillators with Near‐Unity Emission for Ultrahigh‐Resolution X‐Ray Imaging

Abstract Harnessing supramolecular interactions to regulate the structure and performance of functional materials is a key challenge in materials chemistry. Herein, the study utilizes 18‐crown‐6 (18C6) ether‐assisted alkali‐metal (Na, K, Cs) copper(I) iodide supramolecular assemblies to precisely regulate the material structures. This approach facilitated the transition from 1D mono‐royal crown coordination (18C6@KCuI ₂ , CKCI) to 0D di‐royal crown ((18C6) ₂ @Na ₂ (H ₂ O) ₃ Cu ₄ I ₆ , CNCI) and tri‐royal crown ((18C6) ₃ @Cs ₂ Cu ₂ I ₄ , CCCI) structures. Interestingly, the CCCI single‐crystal exhibits outstanding scintillation properties, with a high relative light yield of 71 000 photons MeV ⁻¹ and an ultralow detection limit of 39.3 nGy s ⁻¹ , which can be attributed to the synergistic effects of 18C6 and copper‐iodide clusters. It stabilizes the self‐trapped exciton state, enhances exciton localization, and reduces non‐radiative losses, thus resulting in a large Stokes shift of 193 nm and near‐unity photoluminescence quantum yield of 99.4%. Additionally, 18C6 can promote crystal nucleation and growth, making it easy to prepare centimeter‐scale transparent single crystals with >80% transmittance, such as CCCI single crystal can achieve an ultrahigh‐resolution X‐ray imaging of 26.3 lp mm ⁻¹ . It demonstrates that the structure and performance of halide scintillators can be regulated through supramolecular interactions, which provides a new approach for developing high‐performance scintillator materials.