Molecular Pinning Effect in Composite Self-Assembled Monolayers Enabling Efficient Perovskite/TOPCon Tandem Solar...

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 N₂ atmosphere. Furthermore, the Co-SAM strategy demonstrates excellent generality, boosting the efficiency of 1 cm² TSCs to 32.26% (certified 32.10%). This work offers a versatile interfacial engineering approach toward highly efficient, stable, and scalable perovskite photovoltaics.