Effect of Vacancy-Defect on the Electronic and Optical Properties of Cs₃Cu₂I₅ Scintillators: A First-Principles Study

Lead-free copper-based halide perovskite Cs₃Cu₂I₅ crystals have been recognized as a highly promising material in the field of scintillator materials due to their high quantum yield and fast decay characteristics. Their exceptional optical properties and environmental stability render them highly advantageous for gamma and X-ray detection applications, showcasing significant potential for practical use. To conduct a comprehensive analysis of the impact of irradiation defects on the luminescent performance of Cs₃Cu₂I₅ scintillators and their physical mechanisms, this study employs first-principles methods, focusing on the effects of vacancy defects induced by irradiation on the electronic structure and optical properties of Cs₃Cu₂I₅ crystals. The research finds that Cs and Cu vacancy defects introduce shallow energy levels within the material’s bandgap, thereby expanding the luminescent pathways of the crystal and significantly enhancing the radiative recombination rate. In contrast, I vacancy defects create deep energy levels in the bandgap, functioning as nonradiative recombination centers, thereby suppressing luminescent performance. Furthermore, the presence of I vacancy defects exacerbates the self-absorption of visible light in Cs₃Cu₂I₅ scintillators, resulting in a diminished optical signal reaching the photomultiplier tube, and consequently affecting the overall detection efficiency of the scintillator detector. This study reveals the microscopic mechanisms of damage to Cs₃Cu₂I₅ scintillators under high-energy radiation, offering significant theoretical insights for performance optimization and damage protection in practical applications.