  In this study, combined DFT, SCAPS-1D, and wxAMPS frameworks are used to
investigate the optimized designs of Cs2BiAgI6 double perovskite-based solar
cells. The first-principle calculation is employed to investigate the
structural stability, optical responses, and electronic contribution of the
constituent elements in Cs2BiAgI6 absorber material, where SCAPS-1D and wxAMPS
simulators are used to scrutinize different configurations of Cs2BiAgI6 solar
cells. Here, PCBM, ZnO, TiO2, C60, IGZO, SnO2, WS2, and CeO2 are used as ETL,
and Cu2O, CuSCN, CuSbS2, NiO, P3HT, PEDOT: PSS, Spiro-MeOTAD, CuI, CuO, V2O5,
CBTS, CFTS are used as HTL, and Au is used as a back contact. About ninety-six
combinations of Cs2BiAgI6-based solar cell structures are investigated, in
which eight sets of solar cell structures are identified as the most efficient
structures. Besides, holistic investigation on the effect of different factors
such as the thickness of different layers, series and shunt resistances,
temperature, capacitance, Mott-Schottky and generation-recombination rates, and
J-V (current-voltage density) and QE (quantum efficiency) characteristics is
performed. The results show CBTS as the best HTL for Cs2BiAgI6 with all eight
ETLs used in this work, resulting in a power conversion efficiency (PCE) of
19.99%, 21.55%, 21.59%, 17.47%, 20.42%, 21.52%, 14.44%, 21.43% with PCBM, TiO2,
ZnO, C60, IGZO, SnO2, CeO2, WS2, respectively. The proposed strategy may pave
the way for further design optimization of lead-free double perovskite solar
cells.
