Molecularly Tailored Self-Assembled Monolayers as Hole Transfer Materials Enabling High-Performance Organic Photovoltaics

Interfacial engineering represents a pivotal strategy for enhancing perovskite and organic photovoltaic (OPV) performances. However, conventional interfacial materials face critical limitations in device efficiency and stability, thereby posing great challenges in commercial application. Self-assembled monolayers (SAMs) have demonstrated an exceptional potential as interfacial materials through their unique capabilities in (i) fine-tuning work function, (ii) optimizing bulk-heterojunction morphologies, (iii) surface passivation, and (iv) simultaneously improving device efficiency and stability. By leveraging molecule-tailored interfacial engineering, a simultaneously enhanced interfacial stability, and optimal molecular-level compatibility with photoactive layers can be achieved. This approach can not only improve device performance but also align with the requirements of large-area manufacturing processes. Thus, in this review, we systematically summarize the design rules and performance progress of SAM materials to illustrate the working mechanism and structure–property relationships. Finally, we present an outlook and summary of design principles for SAMs for achieving highly efficient and stable OPVs.