Molecular Pinning Effect in Composite Self‐Assembled Monolayers Enabling Efficient Perovskite/TOPCon Tandem Solar Cells

ABSTRACT Perovskite‐based single junction and tandem solar cells (TSCs) based on self‐assembled monolayers (SAMs) still suffer from interfacial losses related to poor wettability during film formation, defect states of perovskites, and suboptimal energy‐level alignment of devices. Herein, we propose a composite SAM (Co‐SAM) strategy based on tetrahedral‐symmetry‐driven molecular pinning effect of 4,4′,4″,4‴‐methanetetrayltetrabenzoic acid (4MA) with Me‐4PACz for efficient and durable wide bandgap perovskite solar cells (WBG PSCs) and perovskite/TOPCon TSCs. This design enhances monolayer uniformity on NiO x , improves wettability of substrates, and regulates crystallization through Pb‐O coordination and hydrogen bonding, thereby passivating buried‐interface defects and optimizing energy‐level alignment. As a result, inverted 1.68 eV WBG PSCs achieve a champion efficiency of 23.52%, along with impressive stability, retaining over 80% after 1000 h of thermal aging at 85°C in an N 2 atmosphere. Furthermore, the Co‐SAM strategy demonstrates excellent generality, boosting the efficiency of 1 cm 2 TSCs to 32.26% (certified 32.10%). This work offers a versatile interfacial engineering approach toward highly efficient, stable, and scalable perovskite photovoltaics.