Highly Resolved X‐Ray Imaging Enabled by In(I) Doped Perovskite‐Like Cs₃Cu₂I₅ Single Crystal Scintillator

Abstract Low‐dimensional perovskite halides have shown a great potential as X‐ray detection materials because of efficient exciton emissions originating from strongly spatially localized charge carriers. Nonetheless, most of them have a scintillation yield far below their theoretical limits. Here, it is found that the harvesting efficiency of produced charge carriers can be significantly enhanced via a small amount of In + doping in these highly localized structures. A bright and sensitive zero‐dimensional Cs 3 Cu 2 I 5 :In + halide with efficient and tunable dual emission is reported. The radioluminescence emission of Cs 3 Cu 2 I 5 :In + crystals under X‐ray excitation consists of a self‐trapped exciton emission at 460 nm and an In + ‐related emission at 620 nm at room temperature. In + doping enhances the photoluminescence quantum efficiency (PLQY) of Cs 3 Cu 2 I 5 from 68.1% to 88.4%. Benefiting from the higher PLQY, Cs 3 Cu 2 I 5 :In + can achieve an excellent X‐ray detection limit of 96.2 nGy air s −1 , and a superior scintillation yield of 53 000 photons per MeV, which is comparable to commercial CsI:Tl single crystals. As a result, a remarkable X‐ray imaging resolution of 18 line pairs mm –1 is demonstrated, which is so far a record resolution for single crystal perovskite‐based flat‐panel detectors. These results highlight the importance of efficient harvesting of carriers (and excitons) in low‐dimensional perovskites for radiation detection applications.