Mitigating Buried-Interface Energy Losses through Multifunctional Ligands in n–i–p Perovskite/Silicon Tandem Solar Cells

Fabricating efficient monolithic n–i–p perovskite/silicon tandem solar cells remains challenging, as evidenced by substantial recombination losses at the buried interface between the NbO_x electron transport layer (ETL) and perovskite. Herein, we introduce a self-assembled fullerene (C₆₀-SAM) interlayer at this interface, with a large monovalent organic cation incorporated. We find this enhances the surface conductivity of the ETL, mitigates interface recombination, and reduces the energetic mismatch with the overlying perovskite. At the device level, this results in efficient electron extraction and suppressed device hysteresis, substantiated by drift-diffusion simulations. The combination of these improvements led to hysteresis-free n–i–p perovskite/silicon tandem solar cells on textured silicon with an efficiency of 27% (over 1 cm²) and an open-circuit voltage reaching 1.9 V.