Control of droplet morphology for inkjet-printed TIPS-pentacene transistors

We report on methods to control the morphology of droplets of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS-PEN), which are then used in the fabrication of organic thin film transistors (OTFTs). The grain size and distribution of the TIPS-PEN were found to depend on the temperature of the droplets during drying. The performance of the OTFTs could be improved by heating the substrate and also by changing the relative positions of the inkjet-printed droplets. In our experiments, the optimum substrate temperature was 46^oC in air. Transistors with the TIPS-PEN grain boundaries parallel to the current flow between the source and drain electrodes exhibited charge carrier mobilities of 0.44+/-0.08cm^2/Vs.