Air-stable solution-processed n -channel organic thin film transistors with polymer-enhanced morphology

N,N′-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN₂) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN₂ film is much lower than the value of PDIF-CN₂ single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PαMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN₂ thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PαMS or PMMA polymers, the morphology of the PDIF-CN₂ polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm²/V s has been achieved from OTFTs based on the PDIF-CN₂ film with the pre-deposition of PαMS polymer.