A self-assembled monolayer via rapid and scalable soak coating for perovskite solar cells

Abstract

Self-assembled monolayers serve as hole-selective contacts in perovskite solar cells, but their scalable fabrication remains challenging. Here we report a rapid (≤5 min) soak-coating strategy for self-assembled monolayer fabrication, enabled by molecular design and solvent engineering. The unsymmetric self-assembled monolayer material (4-(10-methoxy-7H-benzo[c]carbazol-7-yl)phenyl)phosphonic acid was rationally designed with dual-functional molecular segments to inhibit molecular aggregation in solution and enhance interfacial charge transport. Concurrently, an ethanol-based solvent system containing 1.5 vol% water was engineered to improve material dispersity and strengthen surface anchoring on transparent conducting oxide substrates. The soak-coated self-assembled monolayers exhibit dense and uniform coverage, yielding perovskite solar cells with a certified power conversion efficiency of 27.23%. This methodology demonstrates good scalability, successfully extending to large-area devices, mini-modules and flexible architectures, all of which maintain stable operation. Notably, both the soak-coating solutions and modified transparent conducting oxide substrates can be reused, substantially improving resource efficiency. This work provides a scalable and cost-efficient route for fabricating stable perovskite solar cells. The use of self-assembled monolayers (SAMs) as interfacial hole-selective layers is a key technological enabler for perovskite solar cells (PSCs), but scalable fabrication remains challenging. Here a 5-min soak-coating protocol is developed through SAM molecular design and hydrogen-bond-mediated solvent engineering. High-density monolayers are produced, enabling scalable production of high-efficiency, large-area PSCs.