Afterglow Copper(I) Iodine Cluster Scintillator

Abstract Copper(I) iodine clusters have drawn intense attention due to their advantageous photophysical properties, such as a high luminescence efficiency, large Stokes shift, and tunable luminescence lifetimes. In this work, a copper(I) iodine cluster ( Cu 2 I 2 ‐CH 3 CN ) was synthesized, which exhibits unique afterglow emission, ultrahigh quantum yield (90.1 % in solid state) and aggregation‐induced emission (AIE) behavior. It was found that thermally activated delayed fluorescence (TADF) and long‐lifetime phosphorescence occur simultaneously in Cu 2 I 2 ‐CH 3 CN . The unique photoluminescence properties of Cu 2 I 2 ‐CH 3 CN were attributed to the large spin‐orbit coupling (SOC) and long‐term rigidity of the crystal. The high quantum efficiency, TADF characteristics, and heavy‐atom composition of Cu 2 I 2 ‐CH 3 CN endow it with excellent X‐ray excited luminescence (XEL) properties, making it a promising X‐ray scintillator. A flexible scintillator screen made of Cu 2 I 2 ‐CH 3 CN was successfully fabricated and used for X‐ray imaging with a spatial resolution of 23.6 LP mm −1 .