Study of electronic, optical and photovoltaic properties of lead-free double perovskite Cs2AgXBr6 (X = Bi, Sb): An ab initio calculations

In this work, the electronic, optical, and photovoltaic properties of the two double perovskites were determined, represented, and interpreted using ab initio calculations. The calculations were based on the generalized gradient of Perdew, Burke and Ernzerhof and Tran-Blaha-modified Becke-Johnson approximations within the framework of density functional theory. Quantities that predict the use of dual perovskites in photovoltaic, such as external quantum efficiency, open-circuit voltage and short-circuit current were calculated. These quantities were calculated based on optical properties, in particular the dielectric function, reflectivity, and absorption coefficient. Based on the electronic properties, the gap values obtained with TB-mBJ are 2.13 eV and 1.65 eV, while those obtained with GGA-PBE are 1.48 eV and 1.07 eV for Cs2AgBiBr6 and Cs2AgSbBr6, respectively. The variations in external quantum efficiency and optical absorption coefficient show a strong evolution around the range of energies making up the visible spectrum. This makes them promising materials for the photovoltaic industry. We will apply various pressure values, ranging from 0 to 30GPa, to our structures in order to gain an improved comprehension of the effect of pressure on the energy loss function.