Rigidity‐Regulated Copper(I) Halide Clusters Toward Highly Efficient Photoluminescence and Radioluminescence

Abstract The luminescent efficiency of copper(I) halide cluster‐based complexes is frequently diminished by multiple exciton recombination centers, which significantly restricts their optoelectronic applications. Herein, a mild structural rigidity‐regulation strategy is proposed to suppress exciton recombination by organizing Cu x X x clusters with either the semi‐rigid ligand bis(2‐diphenylphosphinophenyl)ether ( POP ) or the rigid ligand 1,2‐bis(diphenylphosphino)benzene ( dppb ). As a proof of concept, sandwich‐ or butterfly‐like Cu x X x (L) 2 ( x = 2 or 4; X = I or Br, L = POP or dppb ) clusters with different structural rigidity and photoluminescence/radioluminescence performance are synthesized. Compared with Cu 4 I 4 (POP) 2 , the Cu 2 I 2 (POP) 2 and Cu 2 I 2 (dppb) 2 clusters possess higher structural rigidity and form more compact stacks, effectively suppressing structural relaxation‐induced non‐radiative transitions during metal‐to‐ligand or halide‐to‐ligand charge transfer (M/XLCT). Notably, Cu 2 I 2 (POP) 2 and Cu 2 I 2 (dppb) 2 exhibit high photoluminescence/radioluminescence performance, achieving steady‐state X‐ray light yields nearly 150% higher than those of commercial LuAG:Ce. Furthermore, their corresponding flexible films demonstrate outstanding spatial resolution, reaching 11.5 and 14.0 lp mm −1 , respectively. This rigidity‐regulation strategy can open a new avenue for the systematically designing of high‐performance Cu x X x cluster‐based X‐ray scintillators.