Investigation of non-Pb all-perovskite 4-T mechanically stacked and 2-T monolithic tandem solar devices utilizing SCAPS simulation

Abstract

SCAPS simulation was utilized to complement previously published perovskite-on-Si tandem solar devices and explore herein viable all-perovskite 4-T mechanically stacked and 2-T monolithic non-Pb tandem structures. CsSn0.5Ge0.5I3 (1.5\xa0eV) was used as top cell wide bandgap absorber, while CsSnI3 (1.3\xa0eV) was chosen as bottom cell low bandgap absorber. The top cell was simulated with AM 1.5G 1 Sun spectrum, and the bottom cell was simulated with the filtered spectrum from the top cell. To form a 2-T monolithic tandem device, ITO was used as the recombination layer; the current matching condition was investigated by varying the thickness of the absorber layers. For a current-matched device with a Jsc of 21.2\xa0mA/cm2, optimized thicknesses of 450\xa0nm and 815\xa0nm were obtained for the top and bottom absorber layers, respectively. At these thicknesses, the PCEs of the top and bottom cells were 14.08% and 9.25%, respectively, and 18.32% for the final tandem configuration. A much simpler fabricated and simulated 4-T mechanically stacked tandem device, on the other hand, showcased top and bottom cell PCEs of 15.83% and 9.15%, at absorber layer thicknesses of 1300\xa0nm and 900\xa0nm, respectively, and a final overall tandem device PCE of 19.86%.