Recent advances in self-assembled monolayers for perovskite solar cells: from small molecule to polymer

Self-assembled monolayers (SAMs) have emerged as one of the most promising hole-selective materials for inverted perovskite solar cells (PSCs), where their interface regulation capability plays a decisive role in device efficiency and long-term stability. However, conventional small-molecule SAMs suffer from inherent limitations, including insufficient anchoring strength, undesirable molecular aggregation and poor interfacial stability. This review systematically summarizes the interfacial regulation mechanism and the influence of molecular design strategies for small-molecule SAMs with typical anchoring groups. Furthermore, we thoroughly review the recent progress in polymeric SAMs and in situ crosslinked SAMs, with emphasis on their superiority in enhancing interfacial adhesion, solvent resistance, and thermal cycling durability. Finally, the future development directions of SAMs are prospected in terms of large-area and tandem PSCs, aiming to provide insightful guidelines for the design and optimization of next-generation high-performance perovskite photovoltaics.