Lead-based perovskite solar cells exhibit relatively high efficiency, but face toxicity and long-term stability issues, hence, a safer alternative can be lead-free halide perovskites. This research offers a unique and previously unexplored double-absorber perovskite solar cell, employing two high-performing, stable, and lead-free compounds, Cs 2 AgInBr 5 Cl (1.75 eV) and MASnBr 3 (1.3 eV). The well-aligned absorption spectra and band alignment between these absorbers result in high quantum efficiency in the proposed device. A total of fifty-six combinations of fifteen HTLs and ETLs were evaluated, revealing that Cu 2 O paired with TiO 2 delivered the best performance, consistent with band alignment analysis. Our findings reveal that the device performance is strongly affected by the selection of the HTL, defect and acceptor density of the MASnBr 3 layer. Incorporating a graphene interfacial layer between MASnBr 3 and Cu 2 O reduced interfacial recombination, enhanced carrier transportation, and further improved device stability. Through optimization of the structure as FTO/TiO 2 /Cs 2 AgInBr 5 Cl/MASnBr 3 /Graphene/Cu 2 O/Au, we obtained a remarkable power conversion efficiency of 39.44%, a voltage of 1.27 V at open-circuit condition, a current density of 34.538 mA/cm 2 at short-circuit condition, and a fill factor of 89.85%. These results highlight that synergistic absorber matching and proper alignment of the HTL, ETL, and back metal contact with the absorbers are critical for achieving excellent device performance in a stable, non-toxic, and safe structure. Therefore, our achievements, in this research, may lead to the development of innovative optoelectronic devices for the use of renewable solar energy.
Paul et al. (Tue,) studied this question.