Homogeneous Self-Assembled Monolayers Fabricated in Ambient Conditions via Solvent Engineering for Inverted Perovskite Solar Cells

HighlightsWhat are the main findings?This work firstly confirms that ambient humidity remarkably affects the inhomogeneous aggregation of self-assembled monolayers (SAMs).Protic polar solvents cause severe aggregation of SAMs under ambient conditions, while aprotic polar solvents alleviate this defect.The ethanol (EtOH)/N,N-dimethylformamide (DMF) mixed-solvent system enables the fabrication of uniform SAM films and improves interfacial properties.What are the implications of the main findings?Uniform SAM films can be fabricated under humid ambient conditions, which simplifies device preparation conditions.This work provides a feasible ambient fabrication strategy for the industrialization of perovskite solar cells.The solvent engineering offers references for preparing similar self-assembled monolayer systems in ambient air.Benefiting from the booming development of self-assembled monolayer (SAM) based hole-transporting materials, inverted perovskite solar cells (PSCs) have attained a certified power conversion efficiency (PCE) beyond 27.0%, exhibiting great potential for commercialization. However, conventional SAM molecules are prone to self-aggregation owing to their inherent molecular configurations, which readily induced defective and inhomogeneous deposition. In addition, state-of-the-art SAM-based hole-transporting layers are generally deposited in inert environments, while the ambient moisture is expected to further deteriorate the homogeneity of the SAM layers. In this work, a mixed-solvent system of ethanol/N,N-dimethylformamide (DMF) was adopted for the deposition of Me-4PACz SAMs in ambient conditions, which enables significant suppression of intermolecular aggregation in precursor solution and moisture-induced inhomogeneity. The high-quality homogeneous SAM-based hole-transporting layers, along with subsequently optimized perovskite buried interface properties, further empower a prominent increase in the PCE of inverted PSC devices up to 25.0%.