Oriented Molecular Dipole‐Enabled Modulation of NiO_x/Perovskite Interface for Pb‐Sn Mixed Inorganic Perovskite Solar Cells

Abstract Nickel oxide (NiO_x) is considered as a potential hole transport material in the fabrication of lead‐tin (Pb‐Sn) perovskite solar cells (PSCs) for tandem applications. However, the energy level mismatch and unfavorable redox reactions between Ni^≥3+ species and Sn²⁺ at the NiO_x/perovskite interface pose challenges. Herein, high‐performance Pb‐Sn‐based inorganic PSCs are demonstrated by modulating the NiO_x/perovskite interface with a multifunctional 4‐aminobenzenesulfonic acid (4‐ABSA) interlayer. The 4‐ABSA interlayer induces the formation of an oriented dipole moment directed from NiO_x to perovskite, effectively elevating the valance band maximum of the NiO_x film, thus balancing the energy level difference and promoting charge carrier extraction of the device. Moreover, the 4‐ABSA molecules interact with both NiO_x and perovskite, suppressing the reaction of highly active Ni^≥3+ species with perovskites while regulating perovskite crystallization. This results in perovskite films with reduced defect density and enlarged grains. Consequently, a remarkable device efficiency of 17.4% is obtained, representing the highest reported value for Pb‐Sn‐based inorganic PSCs thus far. Furthermore, the 4‐ABSA interlayer enhances the UV‐radiation and operational stability of the resulting devices, maintaining over 80% and 90% of the initial efficiency after 240 h of UV‐light exposure and 480 h of 1 sun illumination, respectively.