Optimization of various terminal topologies of bifacial perovskite/FeSi2 tandem solar cell

Although perovskite (PVK) and bifacial solar cell technologies have gained a rapid emergence in recent years, integration of PVK with low-cost high-efficiency subcell in a bifacial tandem structure is still an area of huge interest. In this work, the potential of FeSi2 thin film solar cell to be used as bottom subcell in a PVK based bifacial tandem cell structure is explored. We use self-consistent electrical-optical model to investigate various terminal topologies of PVK/FeSi2 bifacial tandem solar cell. In particular, we compare a novel three terminal four junction (3T-4J) tandem configuration termed as twin (or double) tandem cell with conventional monolithic two terminal (2T) and mechanically stacked four terminal (4T) bifacial tandem structures having two junction (2J) configuration. We show that the optimal thickness of PVK in 2T-2J tandem configuration is strongly dependent upon magnitude of albedo due to the current-matching constraint between the subcells, whereas both 4T-2J and 3T-4J tandem cells can perform optimally for a broad range of albedo. At optimal cell design, all tandem structures could exhibit efficiency >27.5% at average Earth albedo of ∼30%. Lastly, the results presented in this work provide a complete design space for optimal cell operations and would be beneficial for the development of low-cost high-efficiency PVK based bifacial tandem solar cell.