Enhanced Photoluminescence of Cesium Cadmium Chloride via Cu Doping for X-ray Detection and Anticounterfeiting Applications

All-inorganic Cd-based halides have attracted much interest as a unique class of metal halides because of their afterglow luminescent properties, although the photoluminescence quantum yield (PLQY) is relatively low (<10%). Here, we investigated the optoelectronic characteristics of all-inorganic Cd chloride, including CsCdCl3, Cs2CdCl4, and Cs3Cd2Cl7, and improved their PLQY by Cu(I) doping, achieving a maximal PLQY of 81.6 ± 1.5% for Cs3Cd1.96Cu0.04Cl6.96. Based on the improved optoelectronic properties, we further used them for X-ray detection and anticounterfeiting. Under continuous X-ray irradiation at a dose rate of 26.5 Gy/min for 1800s, the Cu(I) ion-doped Cd chloride exhibits bright luminescence with little intensity loss, indicating high X-ray resistance and stability. As for anticounterfeiting, diversified modes have been fabricated, showcasing the versatile applications of Cd chloride with tunable persistent luminescence in advanced security systems. Our work demonstrates that multimodal luminescence makes Cd-based chlorides suitable as a unique choice among metal halides, extending the applications of metal halides across a wide range of optoelectronic fields.