Promoting Single Channel Photon Emission in Copper(I) Halide Clusters for X‐Ray Detection

Abstract Metal clusters with color‐tunable radioluminescence have attracted growing attention as X‐ray detection materials. However, they are generally less scintillation‐efficient due to the coexistence of multiple exciton recombination centers. Herein, two new zero‐dimensional copper(I)‐based clusters (DIET) 3 Cu 3 X 3 (DIET = 1,3‐Diethyl‐2‐thiourea, X = Cl, Br) are designed, which support the single channel photon emission (Cu cluster centered, CC) to enhance the scintillation performance. Those DIET ligands (L) anchoring with copper(I) ions not only generate direct CuL bonds, but also form a disorder [Cu 3 X 3 ] cluster, which results in the intense X‐ray absorption. (DIET) 3 Cu 3 Br 3 with low halogen electronegativity further weakens halogen‐to‐ligand charge transfer (XLCT) emission, enabling enhanced quantum efficiency (≈69%) and scintillation performance comparable to commercially available Lu 3 Al 5 O 12 :Ce. Moreover, the flexible thin film counterpart demonstrates legible X‐ray imaging with high spatial resolution of 11.71 lp mm −1 . This study provides a feasible design principle to discover new metal cluster‐based scintillators and to further expand their radiation detection applications.