Theoretical Optimization and Comparison of (FA)2BiCuI6 and Cs2AgBi0.75Sb0.25Br6 Based Double Perovskite Solar Cells

Abstract To overcome the issue of toxicity in lead (Pb) based perovskite solar cells, this work investigates, optimizes, and compares the performance of solar photovoltaic cells based on two different promising Pb‐free double perovskite absorber materials viz. (FA) 2 BiCuI 6 and Cs 2 AgBi 0.75 Sb 0.25 Br 6 . The optoelectronic properties of these materials indicate high absorption coefficient with minimum reflection coefficients, making them appropriate for photon absorption. The performance of (FA) 2 BiCuI 6 and Cs 2 AgBi 0.75 Sb 0.25 Br 6 based modeled cells are examined for several combinations of electron and hole transport materials using SCAPS‐1D and the optimized power conversion efficiency (PCE) of 14.3% and 11.1% are achieved by simulating the architectures FTO/SnO 2 /(FA) 2 BiCuI 6 /Cu 2 O/Au and FTO/SnO 2 /Cs 2 AgBi 0.75 Sb 0.25 Br 6 /Cu 2 O/Au, respectively. Further, this work employs the bandgap grading scheme to enhance their PCEs. The efficiency of cells further improves to 14.8% and 12.2% credited to the reduction in interfacial recombination with bandgap graded absorber layers. Moreover, the comparative investigations are also done in terms of absorber layer defect density and working temperature. The findings provide valuable insights into designing of highly efficient Pb‐free double perovskite solar cells as the promising alternative to conventional Pb based halide perovskite photovoltaic cells.