Control of polymorphism and morphology in solution sheared organic field-effect transistors

Despite the high mobility achieved so far with organic molecules, in order to progress in the field it is crucial to find techniques to process them from solution. The device reproducibility is one of the principal weak points of organic electronics for further commercialization. To achieve a high device-to-device reproducibility it is essential to control the morphology and polymorphism of the active layer for OFET application. In this work, we report the preparation of thin films based on blends of the organic semiconductor dibenzo-tetrathiafulvalene (DB-TTF) and polystyrene (PS) by a solution shearing technique compatible with up-scaling. Here, we demonstrate that varying the deposition parameters (i.e., speed and temperature) or the solution formulation (i.e., semiconductor/binder polymer ratio) is possible to control the film morphology and semiconductor polymorphism and, hence, the different intermolecular interactions. We demonstrate that the control of the thermodynamics and kinetics of the crystallization process is key for the device performance optimization. Further, this is the first time that DB-TTF thin films of the α-polymorph are reported.