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 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 (Voc) of 3.080 V. Consequently, this configuration would result in an impressive efficiency of 38.5