Vapor pressure effect on electrical properties of solution-processed organic field-effect transistors

We report the effect of the vapor pressure-dependent solvent evaporation on the electrical performance of solution-processed organic field-effect transistors (OFETs). In our study, a p-type organic semiconductor, 6,13- bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) was used as a soluble active material. For different solvent mixtures of alkane series in anisole, the external pressure of each solvent was varied to control the evaporation rate during the drying process. For twelve types of the OFETs, the electrical characteristics of each type were investigated in terms of the charge carrier mobility and the subthreshold swing in relation to the morphological features of the TIPS-PEN film such as the thickness profile and the domain boundaries. The electrical performance was found to critically depend on the solvent evaporation rate in a combinatorial manner governed by both the vapor pressure of the solvent and the external pressure. The solvent-based approach to the improvement of the film quality of the TIPS-PEN would be directly applicable for fabricating high-performance solution-processed OFETs.