Novel lead-free dual absorber based perovskite solar cells: efficient numerical harnessing towards high efficiency through SCAPS-1D

In the quest for environmentally friendly and highly efficient perovskite solar cells (PSCs). The present study has designed and numerically optimized a novel, cost effective dual absorber FTO/TiO₂/CsSnI₃/Cs₃Sb₂Br₉/Spiro-OMeTAD/Ni. This novel configuration leverages the synergistic properties of narrow bandgap absorber (NBA) CsSnI₃ and wide bandgap absorber (WBA) Cs₃Sb₂Br₉ to broaden the absorption spectrum and enhance device performance. Initial simulations using SCAPS-1D yielded a power conversion efficiency (PCE) of 24.80 %, with an open-circuit voltage (V_oc) of 1.160 V, a short-circuit current density (J_sc) of 26.54 mA/cm², and a fill factor (FF) of 80.50 %. Through systematic optimization of critical device parameters—including absorber layer full thickness, thickness ratio of WBA/NBA, doping densities of absorber and ETL HTL, defect densities, and interface properties—For this attained a peak efficiency of 30.58 %, accompanied by a V_oc of 1.1906 V, a J_sc of 29.8387 mA/cm², and an FF of 86.08 %. According to the latest NREL data, the highest reported efficiency for perovskite solar cells is 26.1 %. Additionally, the impact of back metal contact work function and temperature variations were analyzed and found Nickel (Ni) can be a good alternative to Gold (Au) which gives a good cost-effective solution. Our investigations reveal that a double absorber layer structure, because of broadening the absorption spectrum and enhancing cell stability, outperforms a single-absorber based PSC. These results highlight the potential of our proposed novel combination of bilayer structure to drive the development of lead-free, high-performance PSCs, offering a promising pathway for future experimental validation and large-scale application in sustainable solar energy solutions.