Optimizing Self-Assembled Monolayers via Boronic Acid for High-Performance Inverted Perovskite Solar Cells

Due to the high power conversion efficiency and low fabrication cost, inverted (p–i–n) perovskite solar cells (PSCs) have attracted significant attention in recent years. However, the commonly used self-assembled monolayers (SAMs), such as [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz), tend to aggregate in solution, resulting in inhomogeneous film coverage, which negatively affects perovskite crystallization and overall device performance. To address this issue, we introduce two small-molecule additives─4-methoxyphenylboronic acid (MeO-BOH) and 2-methoxypyridine-5-boronic acid (MeO-N-BOH)─to regulate intermolecular interactions, suppress aggregation, and improve SAM distribution, energy-level alignment, and charge extraction. The optimized interface exhibits a higher work function, reduced interfacial recombination, and a stronger built-in electric field. As a result, the unencapsulated inverted PSCs incorporating MeO-N-BOH achieve a power conversion efficiency (PCE) of 24.75% and retain 80.5% of their initial efficiency after 700 h of maximum power point (MPP) tracking under continuous illumination, significantly outperforming the control devices (PCE = 22.39%). These findings highlight the potential of the boronic acid additive modification strategy in enhancing both the performance and operational stability of PSCs.