Addressing the Optical–Electrical Trade-Off via Rear Polished TOPCon Structures for Efficient Perovskite/Silicon Tandem Solar Cells

Perovskite/silicon tandem solar cells (TSCs) based on tunnel oxide passivating contact (TOPCon) bottom cells are among the most promising pathways toward commercialization, yet their performance is constrained by inadequate passivation in the p -type region of the bottom cell. In this work, we replace the conventional textured rear surface with an alkaline-polished surface, producing a p -type TOPCon structure with substantially enhanced passivation, which yields a high open-circuit voltage of 727 mV in the bottom cell (implied open-circuit voltage ( iV oc ) of the TOPCon precursor is 737 mV). This electrical gain, combined with optical compensation provided by a rear SiN x /Ag reflector, enables the resulting perovskite/TOPCon tandem solar cell to achieve an outstanding open-circuit voltage of 1.964 V and a notable power conversion efficiency of 32.14%.