Upper Subcell Impacts on Perovskite/u-CIGS Tandem Solar Cell Performance

In this paper, the two-terminal perovskite/u-CIGS tandem cells have been numerically performed and studied by using TCAD tools. The investigated planar perovskite model has been performed accordingly in order to match the fabricated structure and to be used as a top cell for tandem cells. The ultrathin CIGS solar cell has been also calibrated according to the fabricated model in order to be used as a good substrate (bottom cell) for the top cell (perovskite). These two cells have been simulated individually and they have revealed an efficiency of up to 20 % and 12.51 % for perovskite and u-CIGS models, respectively. The 2-terminal tandem model is then developed by comprising the top cell with the bottom cell by transparent contact that connects the two sub-cells in series electrically. The influence of changing the defect density in the perovskite film (absorber) and at ETL/absorber and absorber/HTL interfaces on tandem cell characteristics are analyzed. Moreover, we show that the power conversion efficiency of this investigated tandem model can reach over 30% by reducing defect densities and adjusting some sub-cell parameters that were already optimized in our previously published work. These approaches allow us to gain a better understanding of the physical dimensions and defect densities' effect on the performance of the tandem devices.