The manufacture of high-performance electronic devices with micrometre or even submicrometre dimensions by solution processing and direct printing, requires the ability to control accurately the flow and spread of functional liquid inks on surfaces. This can be achieved with the help of surface-energy patterns causing inks to be repelled and dewetted from pre-defined regions of the substrate. To exploit this principle for the fabrication of submicrometre device structures, a detailed understanding of the factors causing ink droplets to dewet on patterned surfaces is required. Here, we use hydrophobic surface-energy barriers of different geometries to study the influence of solution viscosity, ink volume, and contact angle on the process of dewetting of inkjet-printed droplets of a water-based conducting polymer. We demonstrate polymer field-effect transistor devices with channel length of 500 nm fabricated by surface-energy-assisted inkjet printing.

To improve the speed of organic thin-film transistor (TFT) circuits device architectures with submicrometer channel length are of interest. However, in conventional, submicrometer TFT structures the performance is degraded as a result of short-channel effects. Here we present an architecture for short-channel organic TFTs which is based on incorporating an insulating mesa structure in between source and drain electrodes. For submicrometer organic TFTs the mesa structure results in a significant enhancement of the on-off ratio and saturation characteristics. Device modeling shows that the mesa improves the ability of the gate electrode to modulate the carrier concentration in a submicrometer channel.

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