Afterglow Copper(I) Iodine Cluster Scintillator.

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 (Cu2I2‐CH3CN) 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 Cu2I2‐CH3CN. The unique photoluminescence properties of Cu2I2‐CH3CN 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 Cu2I2‐CH3CN endow it with excellent X‐ray excited luminescence (XEL) properties, making it a promising X‐ray scintillator. A flexible scintillator screen made of Cu2I2‐CH3CN was successfully fabricated and used for X‐ray imaging with a spatial resolution of 23.6 LP mm−1. [ABSTRACT FROM AUTHOR]