Orientation-Independent Charge Transport in Single Spherulites from Solution-Processed Organic Semiconductors

Due to the rapidity of morphological development during deposition, solution-processed organic semiconductor thin films exist in semicrystalline or polycrystalline states, incorporating a high degree of local variations in molecular orientation compared to their single-crystal counterparts. Spherulites, a common crystalline superstructure found in these systems, for example, incorporate a large distribution of molecular orientations about the radial axis to maintain their space-filling growth habit. Here, we aim to determine how this distribution of molecular orientations influences charge transport by fabricating arrays of devices on single spherulites. Given that the orientation distribution that is present about the radial axis mandates the presence of low-angle grain boundaries within single spherulites, we find intra-spherulitic charge transport to be independent of the general direction of pi-stacking; organic field-effect transistors exhibit comparable mobilities regardless of how their channels are oriented with respect to the general pi-stacking direction.