Theoretical investigations of double perovskite Rb2AgBiX6 (X = Cl, Br, I) for solar cell and photocatalysis applications

In our work, the lead-free double-perovskite Rb2AgBiX6 (X = Cl, Br, I) has been executed as well as examined by ab-initio computations for solar cell and photocatalytic applications. These results indicate that Rb2AgBiX6 (X = Cl, Br, I) compound has remarkable structural stability and formability, as evidenced by their structural factor, formation energy and mechanical properties. The lower Young's modulus values suggest that these materials can be more easily converted into thin films required for flexible solar cell devices. The calculated bandgap values of Rb2AgBiCl6 (2.86 eV), Rb2AgBiBr6 (2.17 eV) and Rb2AgBiI6 (1.49 eV) disclosed their indirect nature. Moreover, the effective mass of charge carrier in these compounds is relatively small, and the effective mass of hole (mh*) is larger than that of electron (me*), resulting in higher carrier mobility and lower carrier recombination rate. The calculated optical properties indicate that Rb2AgBiX6 (X = Cl, Br, I) has significant light absorption in the ultraviolet and visible light ranges and the absorption peak coefficient can reach ∼105/cm. Finally, the photocatalytic properties are mainly confirmed by the redox potential and carrier recombination rate of these studied materials. Notably, Rb2AgBiCl6 and Rb2AgBiBr6 have better photocatalytic activity. Therefore, theoretical calculations suggest that Rb2AgBiX6 (X = Cl, Br, I) double perovskite has great application potential in solar cell and photocatalytic fields.