Photophysics in Zero‐Dimensional Potassium‐Doped Cesium Copper Chloride Cs3Cu2Cl5 Nanosheets and Its Application for High‐Performance Flexible X‐Ray Detection

• Published in: Advanced optical materials 2022-03, Vol.10 (6), p.n/a
• Main Authors: Han, Lili, Sun, Beibei, Guo, Chao, Peng, Guoqiang, Chen, Huanyu, Yang, Zhou, Li, Nan, Ci, Zhipeng, Jin, Zhiwen
• Format: Article
• Language: English
• Subjects: Broadband; Cesium; Copper chloride; copper halide; Coupling; Crystal lattices; Crystal structure; Dimers; Emitters; environmentally stable; Excitons; flexible devices; Image quality; Lattice parameters; low‐cost; Materials science; Metal halides; Nanosheets; Optical properties; Optics; Photoluminescence; Polystyrene resins; Potassium; Quantum efficiency; Scintillation counters; Spatial resolution; X‐ray imaging
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202102453

Zero‐dimensional Cs3Cu2Cl5 exhibits intriguing optical properties, which can meet the basic requirements of ideal scintillator application. Here, green emitter Cs3Cu2Cl5 nanosheets are successfully synthesized, and by doping with 2% potassium (K+), their photoluminescence quantum yield (70.23% to 81.39%), radioluminescence intensity, and stability are improved. Further experimental and theoretical studies point out that: (1) K+ brings the neighboring [Cu2Cl5]3− dimers groups closer, leading to lattice shrinkage and lower lattice constants; (2) such compact crystal structure results in stronger exciton–photon coupling and reduced phonon–electron coupling strength, which is beneficial to form self‐trapped excitons and enhanced luminescence; (3) lower lattice constants also induce decreased bandgap (2.58 to 2.51 eV) and increased Stokes shift (217 to 223 nm), for less self‐absorption and higher quantum efficiency. Finally, area‐controllable uniform flexible Cs3Cu2Cl5:2%K+–polystyrene film is successfully achieved with excellent X‐ray sensibility. Such flexible film shows low cost (2.8223 $/g), broadband response (20–160 keV), and high spatial resolution (5 lp mm−1) that is comparable to commercial CsI:Tl wafer. Moreover, it fits well with nonplanar surfaces for high‐quality medical and industrial flexible images applications. It is believed that this work can provide a viable tactic to enhance X‐ray detection in metal halide scintillators. Cs3Cu2Cl5:2%K+ nanosheets present 81.39% photoluminescence quantum yield, high radioluminescence intensity, and excellent air stability. Meanwhile, the area‐controllable Cs3Cu2Cl5:2%K+‐polystyrene film as flexible X‐ray imaging screen is obtained with low cost (2.8223 $ g−1), broadband X‐ray response (20–160 keV), high spatial resolution (5 lp mm−1), and ultra‐tenacity (300 times bends), and fits well with nonplanar surfaces for high‐quality flexible images applications.