Device optimization of FASnI₃ / MAPbI₃ tandem solar cells: evaluating carrier recombination and engineering parameters for high PCE

This study introduces the design and optimization of a perovskite-–perovskite tandem solar cell (PPTSC) composed of all perovskite absorber materials. The optimization process involved individual tuning of top and bottom perovskite solar cells, comprising MAPbI₃ and FASnI₃, respectively. Various material properties, including thickness, electrical characteristics, and recombination mechanisms such as radiative recombination, Auger electron, Auger hole, and band-to-band recombination, have been systematically tuned. After optimizing each subcell independently, the standalone subcells have been then integrated into PPTSC. The optimum PPTSC thickness has been determined by achieving a matching current for each subcell. By changing each subcell's thickness, a current matching \({J}_{sc}\) $J_{\mathit{sc}}$ of 13.4 mA/cm² has been achieved with a 135 nm top subcell thickness and a bottom subcell thickness of 400 nm. Under these conditions of current matching, the designed device indicated that the tandem cell would exhibit a notably enhanced voltage in the open circuit (V_oc) of 3.080 V. Consequently, this configuration would result in an impressive efficiency of 38.5%, surpassing the individual efficiencies of each subcell.