Optimization of a Pb-free all-perovskite tandem solar cell with 30.85% efficiency

We present simulation results obtained with the SCAPS-1D simulation package of a lead-free all-perovskite tandem solar cell. The top and bottom subcells, consisting of MAGeI3, and FASnI3, respectively, were optimized individually by varying material properties such as thickness, electron affinity, and capture cross-section. These standalone optimized subcells are then utilized for the tandem structure. The optimal tandem cell thickness was determined based on short circuit current density (JSC) matching of the standalone subcells by varying the subcells’ thickness. A matching JSC of 14.70 mA/cm2 was obtained for the top and bottom subcell thickness of 983 nm and 1600 nm, respectively. At this current matching condition, the simulation show that a tandem cell would yield a high open-circuit voltage (VOC) of 2.63 V, resulting in an efficiency of 30.85%, significantly higher than that of each subcell.