Eliminating Texture‐Induced Retention of Self‐Assembled Monolayer Residues for High‐Performance Perovskite Solar Cells

Abstract

Self-assembled monolayers (SAMs) constitute foundational interfacial elements in high-efficiency inverted perovskite solar cells (PSCs); however, ensuring chemical and electronic integrity across SAM-modified interfaces remains challenging. Although post-deposition solvent washing has been widely applied to remove loosely bound or aggregated SAM species, its topography-dependent consequences for SAM-modified textured FTO, including retention and solvent-dependent removal, have not been systematically examined. Here, we identify texture-induced retention of π-π-stacked SAM aggregates within nanoscale valleys of FTO, rendering them resistant to conventional alcohol-based washing. To address this limitation, we establish a substrate-informed solvent engineering strategy that balances removal of SAM aggregates with preservation of chemisorbed SAMs. Complementary crystallographic and theoretical analyses reveal that N, N-dimethylformamide (DMF) provides the most balanced solvent-SAM interaction window among examined solvents, enabling removal of valley-retained residues while maintaining the chemisorbed SAM interface. The resulting interfacial refinement establishes a homogeneous electrostatic landscape and improved energy alignment at the perovskite/SAM interface, while serving as a uniform growth template for high-quality, strain-relieved perovskite films. Consequently, DMF-washed devices achieve a power conversion efficiency of 26.13% (certified 25.82%) and demonstrate enhanced stability under illumination and thermal stress. These findings highlight substrate-informed solvent washing as a reliable strategy for SAM-based interfacial engineering on textured electrodes.