Solution-Processable NiO x :PMMA Hole Transport Layer for Efficient and Stable Inverted Organic Solar Cells.

For organic solar cells (OSCs), nickel oxide (NiO x ) is a potential candidate as the hole transport layer (HTL) material. However, due to the interfacial wettability mismatch, developing solution-based fabrication methods of the NiO x HTL is challenging for OSCs with inverted device structures. In this work, by using N, N-dimethylformamide (DMF) to dissolve poly(methyl methacrylate) (PMMA), the polymer is successfully incorporated into the NiO x nanoparticle (NP) dispersions to modify the solution-processable HTL of the inverted OSCs. Benefiting from the improvements of electrical and surface properties, the inverted PM6:Y6 OSCs based on the PMMA-doped NiO x NP HTL achieves an enhanced power conversion efficiency of 15.11% as well as improved performance stability in ambient conditions. The results demonstrated a viable approach to realize efficient and stable inverted OSCs by tuning the solution-processable HTL.