Self-Assembled Monolayers at Photovoltaic Interfaces: Unveiling Structure–Property Relationships to Applications in Perovskite and Organic Solar Cells

Although the optimized structures of the photoactive species have driven a rapid development in third-generation solar cells in the past decade, minimizing interfacial loss is another critical factor for achieving high-performance devices. Self-assembled monolayers (SAMs) have emerged as an effective approach to modulate the interface between materials to enhance device performance and stability, serving as alternatives to the conventional polymeric hole-transporting layers. In this Review, we first provide a systematic analysis on each structural component of SAMs, while elucidating the underlying mechanisms of their characteristic advantages. Furthermore, we investigate their applications in both perovskite solar cells and organic photovoltaics, emphasizing their role in highly efficient solar cells. Finally, we propose the future research direction of the field for large-scale manufacturing and commercialization. The structure-property relationships discussed in this Review will serve as a foundation for the optimized designs of SAMs, offering insights into achieving theoretical limits in next-generation devices.