RESUMO
Ab initio calculations have been used to investigate lead-free double-perovskites (DPs) X2AgBiY6 (X = NH4, PH4, AsH4, SbH4 and Y = Cl, Br) for solar-cell-based energy sources. The most recent and improved Becke-Johnson potential (TB-mBJ) has been proposed for the computation of optoelectronic properties. Theoretical and calculated values of the lattice constants obtained by applying the Wu-Cohen generalized gradient approximation (WC-GGA) were found to be in good agreement. The computed bandgap values of (NH4)2AgBiBr6 (1.574 eV) and (SbH4)2AgBiBr6 (1.440 eV) revealed their indirect character, demonstrating that they are suitable contenders for visible light solar-cell (SC) technology. Properties like the refractive index, light absorption, reflection, and dielectric constant are all explained in terms of the optical ranges. Within the wavelength range of 620-310 nm, the maximum absorption band has been identified. Additionally, we discover that all chemicals investigated herein have photocatalytic capabilities that can be used to efficiently produce hydrogen at cheap cost using solar water splitting by photocatalysts. In addition, the stability of the compounds was examined using the calculation of mechanical properties.