TOPCon-based bottom cells for perovskite/silicon tandem solar cells

The drive toward higher solar cell efficiencies and a lower levelized cost of electricity is accelerating the research and development of perovskite/silicon tandem solar cells. Silicon heterojunction (SHJ) bottom cells have traditionally dominated perovskite/silicon tandem research due to their high open-circuit voltages ( V oc ) (>740 mV) and integration flexibility. However, recent advances in conventional tunnel oxide passivated contact (TOPCon) solar cells, including improvements in front-side passivation, doped poly-Si contact optimization, and laser-assisted firing technologies, have significantly narrowed the V oc gap, a trend that is increasingly reflected in the growing number of TOPCon-based tandem studies. In this work, we review the current status of TOPCon-based bottom cells for perovskite/silicon tandem integration, benchmarking them against SHJ-based tandems in terms of efficiency potential, manufacturability, cost, and scalability. Although certified efficiencies of TOPCon-based tandems still lag their SHJ counterparts, preliminary simulations predict that TOPCon-based tandems can achieve comparable power conversion efficiencies with SHJ-based tandems. A techno-economic analysis indicates that TOPCon's lower fabrication costs may offer critical advantages for mass and sustainable tandem production. Furthermore, we explore recent advances in process adaptations, including textured surface optimization, atomic hydrogenation, the development of transparent conductive oxide (TCO)-free interconnect layers, and bi-poly TOPCon structures, which collectively enhance the industrial feasibility of TOPCon-based tandem architectures. Finally, we identify key challenges, such as parasitic absorption, surface passivation losses on textured surfaces, sputter-induced damage, and dehydrogenation of TOPCon bottom cells.