Computational Investigations on Viability of Inorganic Cs 2 AgBiI 6 Double Perovskite Semiconductor for Hybrid Solar Cell Modules

The structural, electronic, and optical properties of lead-free double perovskite Cs 2 AgBiI 6 were investigated using density functional theory (DFT) within the generalized gradient approximation (GGA) implemented in Quantum ESPRESSO. Cs 2 AgBiI 6 exhibits an indirect band gap, with the valence band maximum and conduction band minimum located at different high-symmetry points. Structural stability was assessed using convex hull analysis and the Goldschmidt tolerance factor, while optical calculations revealed strong visible-light absorption. The obtained material parameters were subsequently employed to design a hybrid solar cell with the configuration Au/Spiro-OMeTAD/Cs 2 AgBiI 6 /CIGS/CdS/TiO 2 /FTO using SCAPS-1D. The optimized device achieved a power conversion efficiency of 44.86%, with an open-circuit voltage of 1.092 V, short-circuit current density of 49.98 mA/cm 2 , and fill factor of 82.11%. PVsyst simulations yielded a maximum module power of 1025.9 W at 1000 W/m 2 irradiance, demonstrating the potential of Cs 2 AgBiI 6 for efficient lead-free photovoltaics.