First-principles simulation study on the impact of monovalent Cu ion doping on the crystal structure and electrical properties of lead-free perovskite Cs2AgBiBr6

[Background]: The lead-free double perovskite Cs2AgBiBr6 has garnered extensive attention in the field of nuclear radiation detection as an environmentally friendly material. Experimental observations have revealed that doping Cs2AgBiBr6 with Cu+ significantly enhances the material's stability and photoelectric conversion efficiency. [Purpose]:The study aims to investigate the impact of Cu+ doping on the crystal structure and electrical properties of Cs2AgBiBr6.[Methods]: Using first-principles calculations based on density functional theory, a simulation study was conducted to explore the effects of Cu+ doping on the structure and electrical properties of Cs2AgBiBr6.[Results]: The results indicate that Cu+ doping enhances the stability of Cs2AgBiBr6. The Cs2Ag1-xCuxBiBr6 compounds formed by doping, as well as the original Cs2AgBiBr6 material, exhibit an indirect bandgap semiconductor behavior. The bandgap significantly narrows with an increase in the Cu+ doping ratio. Analysis of the density of states (DOS) suggests that the bandgap narrowing is attributed to the downward shift of the conduction band minimum dominated by Bi 6p orbitals due to Cu+ doping.[Conclusions]: Cs2Ag1-xCuxBiBr6 exhibits higher stability and superior electrical properties compared to Cs2AgBiBr6. It emerges as a promising candidate material for semiconductor radiation detectors.