Simulation of Optimized High-Current Tandem Solar-Cells With Efficiency Beyond 41%

Two-terminalt and tandem solar-cells have a high efficiency of power conversion. One of their main limitations is the operating current density as the two-terminal tandem solar-cell is equivalent to electrically connected series subcells. Increasing the top absorber layer's thickness will lead to an increase in the top subcell current and a decrease in the bottom subcell's current. The subcell with the minimum current forces the tandem cell to operate at its value, limiting the overall performance. In this paper, a proposed solution for such a problem is introduced using a bottom subcell consisting of germanium-telluride (GeTe), which gives a high current and matches the top subcell at a thicker absorber layer. A proposal of three different tandem cells with perovskite (MAPbI(3))/CIGS, perovskite (MAPbI(3))/GeTe, and perovskite (MAPbI(3-x)Cl(x))/GeTe have been presented. The proposed perovskite (MAPbI(3))/CIGS has an efficiency of 30.52%, whereas the replacement of the CIGS bottom subcell by GeTe led to a significant enhancement of the efficiency to reach 35.9%. High efficiency of 41.7% is obtained by replacing the perovskite (MAPbI(3)) top subcell with perovskite (MAPbI(3-x)Cl(x)). A modified numerical algorithm is proposed to obtain the optimum thickness of the top subcell to achieve higher power-conversion efficiency. The performance evaluation and simulation of the designed tandem cells were carried out using SCAPS-1D. The temperature effects on the proposed cells have been encountered in simulation. The results show that the proposed tandem solar-cells have comparable performance and higher efficiencies relative to the published works.

Automated summary

This paper introduces a proposed solution to the restrictions of operating current density in tandem solar cells by using GeTe as the bottom subcell, balancing the efficiency. Three different tandem cell configurations were presented, showing that replacing the bottom subcell can significantly enhance efficiency.