Optoelectronic and photovoltaic properties of Cs2AgBiX6 (X = Br, Cl, or I) halide double perovskite for solar cells: Insight from density functional theory

In this study, the electronic structure, optical, and electrical properties of double perovskite Cs2AgBiX6 (X = Br, Cl, and I) were investigated through the density functional theory within the Tran-Blaha modified Becker-Johnson approach. The optoelectronic properties such as the bandgap energy, density of states, charge density, and dielectric function are discussed. The physical parameters including the quantum efficiency, V-oc, J(sc), were estimated for industrial photovoltaics (PV). Based on the optimized structure, it was found that the bandgap values are 1.12, 2.04, and 2.81 eV for Cs2AgBiI6, Cs2AgBiBr6, and Cs2AgBiCl6 respectively. Meanwhile, the electronic charge density predicts that the bounds between Cs and Br/I/Cl are covalent. Quantum efficiency shows high evolution, a very high spectrum of absorption coefficients is observed around the visible range, which proves the use of such double perovskite compound in the PV device.