(714c) Tuning Charge Transport of Solution Sheared Organic Semiconductors Using Lattice Strain

Solution deposition of organic semiconductors (OSC) is a leading contender for producing large-area, inexpensive, and flexible organic electronics. We recently developed a solution deposition method for OSCs known as solution shearing, which resulted in better organic field effect transistor (OFET) performance compared to those fabricated from simple drop casting or spin casting methods. We found that this method can achieve a wide range of reproducible OSC morphologies, which results in differing FET performance. We measure the molecular ordering resulting from a variety of solution shearing conditions, and we show that we can controllably tune the molecular packing of OSCs by generating lattice strain in the growing crystalline thin film. We discuss the characteristics of this method and its applicability to a wide range of OSCs. Using the OSC TIPS-pentacene as a model, we show that certain conditions yield remarkable FET performance, where FETs show an average charge carrier mobility around 2 cm² V^-1s^-1 with some transistors showing mobilities as high as 4 cm² V^-1s^-1, a current On/Off ratio of  > 10⁶, low hysteresis and a low threshold voltage.  We also investigate the thermal and temporal stability of the lattice strained TIPS-pentacene crystalline films, and measure the relationship between the morphological features and its impact on carrier charge transport.