Temperature‐Inert Coinage Metal Cluster Scintillator

Abstract Scintillators can convert high‐energy ionizing radiation, such as X‐ray, into low‐energy ultraviolet‐visible photons, and they have been widely used in various fields. However, like most luminogens, the emission intensity of a scintillator is usually influenced by the environmental temperature, increasing the temperature results in extreme decreases in radioluminescence. Here, a temperature‐inert coinage metal cluster scintillator of Cu 4 S was prepared, and it exhibited not only intense radioluminescence at room temperature but also minimal fluctuations from 80 to 450 K. Mechanism study revealed that Cu 4 S is a typical thermally activated delayed fluorescence (TADF) luminogen. Owing to the strong C─H··· π interactions between the clusters, the geometric relaxation of Cu 4 S was restricted during the spin crossover process, leading to an exceptionally small reorganization energy. This induced intersystem crossing within the Marcus inverted region, resulting in temperature‐independent luminescence behavior. More importantly, Cu 4 S metal cluster has excellent water‒oxygen stability and thermal stability and can be used to prepare flexible scintillator screen with polydimethylsiloxane (PDMS). On the basis of these features, temperature‐independent high‐resolution X‐ray imaging with the Cu 4 S ‐PDMS scintillator screen was achieved, and the resolution at different temperatures was maintained above 20 LP mm −1 .