Synergistic Hole Extraction and Defect Passivation via Co‐Assembled Monolayers for Efficient Wide‐Bandgap Perovskite and Tandem Solar Cells

ABSTRACT Incomplete surface coverage and weak end‐group interactions with perovskites in widely employed self‐assembled molecules (SAMs) pose a significant challenge to advancing perovskite photovoltaic devices, which is even more pronounced in perovskite/silicon tandem solar cells (PSTSCs). Herein, we implement a strategic co‐self‐assembled monolayers approach by introducing a bifunctional interconnector, 4‐nitrophenylboronic acid (NPBA), atop the NiO x /SAM film surface to strengthen the interfacial connection between the substrate and perovskite layer, while simultaneously suppressing the energy losses at the NiO x /SAM/perovskite interfaces. Robust anchoring of NPBA to the NiO x surface is achieved through synergistic interactions of its electron‐withdrawing nitro group (−NO 2 ) and electron‐donating boronic acid group (−B(OH) 2 ) with the exposed NiO x regions not covered by SAMs. This dual binding effectively suppresses the defects of NiO x and lowers its valence band, thereby enhancing hole selectivity. Furthermore, the synergistic passivation effect of −NO 2 and −B(OH) 2 groups contribute to highly passivated perovskites with healed Pb−Pb dimers and the iodide vacancies. As a result, the NPBA‐incorporated wide‐bandgap perovskite solar cells, featuring a bandgap of 1.7 eV, achieve a high power conversion efficiency (PCE) of 21.46%. Building on this, a maximum PCE of 31.28% with excellent operational stability is obtained in PSTSCs.