Macroscopic Alignment of One-Dimensional Conjugated Polymer Nanocrystallites for High-Mobility Organic Field-Effect Transistors

Abstract

Controlling the morphology of polymer semiconductors remains a fundamental challenge that hinders their widespread applications in electronic and optoelectronic devices and commercial feasibility. Although conjugated polymer nanowires (NWs) are envisioned to afford high charge-carrier mobility, the alignment of preformed conjugated polymer NWs has not been reported. Here, we demonstrate an extremely simple and effective strategy to generate well-aligned arrays of one-dimensional (1D) polymer semiconductors that exhibit remarkable enhancement in charge transport using a solution shear-coating technique. We show that solution shear coating of poly(alkylthiophene) NWs induces extension or coplanarization of the polymer backbone and highly aligned network films, which results in enhanced intra- and intermolecular ordering and reduced grain boundaries. Consequently, highly aligned poly(3-hexylthiophene) NWs exhibited over 33-fold enhancement in the average carrier mobility, with the highest mobility of 0.32 cm(2) V(-1) s(-1) compared to pristine films. The presented platform is a promising strategy and general approach for achieving well-aligned 1D nanostructures of polymer semiconductors and could enable the next generation of high-performance flexible electronic devices for a wide range of applications.

Conjugated polymer single crystals and nanowires

“…Egap et al and Reichmanis et al prepared ordered P3HT nanowires almost simultaneously by offering a shear force during the film forming process . Figure A shows the schematic diagram of nanowire films deposited on an FET device substrate with a shear force . Egap et al found that P3HT nanowires achieved the best order when the shearing speed was approximately 2 mm/s, as shown in Figure B.…”

“…Thus, the mobility of nanowire film TEF is much lower than that of single crystal or nanowire FET. Egap et al and Reichmanis et al prepared ordered P3HT nanowires almost simultaneously by offering a shear force during the film forming process . Figure A shows the schematic diagram of nanowire films deposited on an FET device substrate with a shear force .…”

“…(B) AFM images of the resulting poly(3‐hexyl thiophene) (P3HT) nanowire films under different shearing speeds. (Adapted from Reference with permission from Copyright 2016 American Chemical Society)…”

Liquid Crystal Ordering on Conjugated Polymers Film Morphology for High Performance

“…Thus far, two strategies have been proposed to solve this problem. Experiments demonstrated that the formation of a proper amount of preaggregates leads to less relaxation behavior and that an external force could align these aggregates and maintain this structure, which could further grow during the film drying process . However, this strategy encounters problems in that the orientation direction of the final film is determined by the long axis of the preaggregates or nanofibers, and the aspect ratio and chain mobility are decreased by the formation of aggregates .…”

Solving Materials’ Small Data Problem with Dynamic Experimental Databases

“…Ideally, an influential design variable should be able to be varied independently from other process conditions. Recent advances in blade and shear coating techniques, currently not captured by the database, offer a promising approach to independently control the film thickness to explore its impact on charge carrier mobility [49,50].…”