Sequential Vacuum Evaporated Copper Metal Halides for Scalable, Flexible, and Dynamic X‐Ray Detection

Abstract Copper metal halides have emerged as a strong contender in the scintillator field due to the self‐trapped excitons (STEs) mechanism. However, their development has been hindered by the preparation process. Single crystals have long growth cycles and cannot achieve large areas and flexibility. Quantum dots have a low yield and can easily cause chemical pollution, and the thickness of films prepared by the spin coating cannot be controlled. To address these challenges, a new method for preparing Cs₃Cu₂Cl₅ using sequential vacuum evaporation is developed. This allows successful preparation of large‐area (≈100 cm²) and flexible films. The STEs mechanism of Cs₃Cu₂Cl₅ gives it unique properties such as a large Stokes shift that reduces self‐absorption effects, and a wide full width at half‐maximum that improves coupling with photodiodes. Therefore, Cs₃Cu₂Cl₅ is applied to X‐ray imaging with a light yield of ≈30 000 photons MeV⁻¹, a spatial resolution of over 10 lp mm⁻¹, and a low detection limit below 0.8 µGy_air s⁻¹. In addition, the flexible Cs₃Cu₂Cl₅ film enables effective dynamic imaging and clear imaging on non‐planar objects. It also exhibits good resistance to harsh environments, maintaining good imaging performance after 150 days. It is believed that sequential vacuum evaporation provides an important idea for preparing scintillators.