Recent demonstration of mobilities in excess of 10 cm2/Vs have energized research in solution deposition of polymers for thin film transistor applications. Due to the pi-stacking motif of most semiconducting polymers, the local mobility is expected to be intrinsically anisotropic. Fabrication of oriented films enables further optimization of device performance and can enable detailed structural characterization. Blade coating is an excellent prototyping tool for production deposition techniques such as slot die coating. Unlike slot die coating, a pre-metered technique, blade-coating is a self-metered technique and there exist two distinct operational regimes: the Landau-Levich or horizontal dip coating regime and the evaporative regime. We report results from blade coating a number of high performing polymer materials on unpatterned and nano-structured[1] substrates. Depending on polymer and deposition regime, oriented films can be produced on unpatterned substrates. In general, the orientation appears nucleated at the air interface as bottom contact devices exhibit isotropic transport. In all cases, nano-structured substrates produce anisotropic bottom contact devices with the polymer chain oriented along the groove direction. This allows the opportunity to create twisted films, analogous to liquid crystal displays. Detailed structural analysis (UV-Vis, FTIR, GIXD) and transport (channel, contact resistance) results will be presented.
1. Tseng, H.-R., et al., Nano Letters 2012, 12, 6353-6357.