Influence of phase-separated morphology on small molecule/polymer blend organic field-effect transistors fabricated using electrostatic spray deposition

Bottom-gate top-contact organic field-effect transistors (OFETs) based on 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) and poly(methyl methacrylate) (PMMA) blends were fabricated using electrostatic spray deposition (ESD). Solvent-vapor annealing (SVA) was conducted as a post-deposition treatment to induce vertical phase separation of the blend films. The phase-separated morphology was investigated by selective etching of TIPS pentacene with cyclohexane. A relatively rough surface with some pinholes was observed in the etched film without SVA, suggesting that vertical phase separation was not sufficient during the ESD process. The phase-separated morphology was modified remarkably by SVA, and a SVA-treated blend device with a well-defined phase-separated structure exhibited enhanced performance and operational stability compared to a device based on the as-deposited blend.