Solution-Processed Molybdenum Oxide with Hydroxyl Radical-Induced Oxygen Vacancy as an Efficient and Stable Interfacial Layer for Organic Solar Cells

The interfacial layer (IL) in organic solar cells (OSCs) can be an important boosting factor for improving device efficiency and stability. Herein, a facile and cost-effective approach to form a uniform molybdenum oxide (MoO3) film with desirable stability is provided, based on solution processing at low temperatures by simplified precursor solution synthesis. The solution-processed MoO3 (SM) film, with oxygen vacancies induced by the hydroxyl group, functions as an efficient anode IL in conventional OSCs. The hole-transporting performance of SM is well demonstrated in nonfullerene-based OSCs exhibiting over 10% of power conversion efficiency. The enhanced device performance of SM-based OSCs over that of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is investigated by analyzing the morphology, electronic state, and electrical conductivity of such a hole-transporting layer, as well as the charge dynamics in the completed devices. Furthermore, the high stability of the SM films in OSCs is examined under various environmental conditions, including long-term and thermal stability. In particular, fullerene-based OSCs with SM maintain over 90% of their initial cell performance over 2500 h under inert conditions. It is shown that solution-processed metal oxides can be viable ILs with high functionality and versatility, overcoming the drawbacks of conventionally adopted conducting polymer interlayers.