Thermal Crosslinking Dual‐Anchor Self‐Assembled Monolayers for Improved Interfacial Hole Transport and Perovskite Photovoltaic Stability

ABSTRACT Nickel oxide (NiO _x ) based hole‐transport material (HTM) has been extensively used in inverted structured perovskite solar cells (PSCs) but suffers from interfacial energy mismatch and defect‐driven recombination, thus lower power conversion efficiency (PCE). Herein, we have designed low‐cost cross‐linkable self‐assembled monolayers (SAMs) including single‐anchoring 4′‐(bis(4‐vinylphenyl)amino)‐[1,1′‐biphenyl]‐4‐carboxylic acid ( p ‐TPA) and dual‐anchoring 4′‐(bis(4‐vinylphenyl)amino)‐[1,1′‐biphenyl]‐3,5‐dicarboxylic acid ( m ‐TPA) to address these intrinsic issues. Results of theoretical calculations and experimental characterizations have shown that m ‐TPA modulation enhanced bidentate binding onto NiO _x , leading to a favorable highest occupied molecular orbital (HOMO) and an optimized molecular geometry. The thermal cross‐linked m ‐TPA demonstrated higher surface coverage, superior interfacial passivation on NiO _x and an optimal Ni ² ⁺ fraction. The dual‐anchor modified NiO _x HTLs exhibited largely reduced perovskite permeation and higher surface electrical conductivity. Consequently, m ‐TPA‐modified PSCs achieved a champion power conversion efficiency (PCE) of 24.16%, which is much higher than pristine NiO _x ‐based (18.98%) and mono‐anchor crosslinked modified ones (22.13%). The PSCs with cross‐linked m ‐TPA modification also exhibited substantially reduced hysteresis and significantly improved device operational stability under environmental/irradiation stress. This work demonstrates the potential of thermal crosslinking SAMs with dual‐anchor molecular engineering as an effective strategy to concurrently optimize charge extraction and interfacial resilience in PSCs.