Potassium-regulated lead-free cesium copper iodide CsCuI perovskites with enhanced scintillation properties and their application in high-resolution X-ray imaging

Ternary copper halides, such as Cs 3 Cu 2 I 5 , as an emerging class of nontoxic alternatives to lead halide perovskites, have drawn extensive attention in the X-ray detection field due to their efficient self-trapped exciton emissions. However, the light yield far below the theoretical limit seriously hinders the high-resolution X-ray detection application of copper halide scintillators. Herein, Cs 3 Cu 2 I 5 :K + scintillation films and single crystals with enhanced photoluminescence (PL) and radiation luminescence (RL) were first obtained by adjusting the doping concentration of K + ions in the 0-8 at% range. The substitution of Cs + by doping K + compacted the adjacent [Cu 2 I 5 ] 3− dimer groups, resulting in a stronger exciton-photon coupling strength. Therefore, Cs 3 Cu 2 I 5 :K + single crystals exhibited a stronger RL emission under X-ray excitation, and their light output was about 49.6% higher than that of the pure Cs 3 Cu 2 I 5 , with an accelerated scintillation decay time (330 to 241 ns). Benefiting from these advantages, X-ray detectors based on hydrophobic polymethyl methacrylate (PMMA)-coated Cs 3 Cu 2 I 5 :K + flexible films could deliver a higher X-ray imaging resolution of 11.7 lp mm −1 @MTF = 0.2 in comparison with the commercial gadolinium oxysulfide (GOS)-based detectors (6.2 lp mm −1 @MTF = 0.2). This work provides insights for the design of metal halides for use in low-cost and high-resolution flexible X-ray imaging systems. Potassium doping regulation significantly enhances the scintillation performance of Cs 3 Cu 2 I 5 perovskite single crystals with blue light emission.