Lead-free All-perovskite Tandem Solar Cell

We simulated a lead-free all-perovskite tandem solar cell using the SCAPS-1D simulation tool. The purpose of this work is to assess the performance of alternatives to lead-based perovskite in a tandem structure. First, the top and bottom subcells, consisting of MAGeI$_3$, and FASnI$_3$, 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 final tandem cell thickness was determined based on short circuit current density (J$_{\text{SC}}$) matching of the standalone subcells by means of varying the thickness of the subcells. A matching J$_{\text{SC}}$ of 14.75 mA/cm$^2$ was obtained for the top and bottom subcell thickness of 970 nm and 1400 nm, respectively. At this current matching condition, the tandem cell yielded a very high open-circuit voltage (V$_{\text{OC}}$) of 2.63 V, resulting in an efficiency of 30.89\% which is significantly higher than that of the single junction.