Vapor‐Deposited Copper Iodide Cluster Scintillators for High‐Resolution X‐Ray Imaging

Copper(I) iodide (CuI) clusters are promising x‐ray scintillators due to their eco‐friendliness, low cost, and easy processability. However, solution‐processed films suffer from poor uniformity and significant light scattering due to solvent evaporation, limiting spatial resolution and monolithic integration. Herein, we developed monolithically integrated cluster scintillator films via vacuum co‐evaporation. We designed a CuI cluster scintillator, ([ para Cz‐Py] 4 Cu 2 I 2 ), fabricated via co‐evaporation. By strategically modulating the carbazole substituent sites (para, meta, and bimeta), the para‐substituted configuration ([ para Cz‐Py] 4 Cu 2 I 2 ) significantly optimizes optical properties compared to its analogues. Specifically, the [ para Cz‐Py] 4 Cu 2 I 2 cluster achieves a minimized singlet‐triplet energy gap () of 0.033 eV and a high photoluminescence quantum yield (PLQY) of 98%. Consequently, the [ para Cz‐Py] 4 Cu 2 I 2 cluster scintillator delivers a light yield of 14 000 photons·MeV −1 and a decay time of 14.5 ns. Furthermore, benefiting from the superior homogeneity and dense morphology provided by the thermal evaporation process, the films exhibit superior x‐ray imaging capabilities with a high spatial resolution of 17.5 lp·mm −1 , which is significantly higher than that of typical solution‐processed cluster films. This work provides insights into developing next‐generation, environmentally friendly, and high‐resolution cluster scintillators through ligand‐modulated engineering.