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.