Uniform, high performance, solution processed organic thin-film transistors integrated in 1 MHz frequency ring oscillators

Organic electronics is one of the most promising technologies for creating flexible electronic devices using low temperature plastic compatible processes. However, contact resistances of organic transistors remain one of the most significant hurdles to achieving high performance circuits in this technology. Short channel devices (< 10 mu m), essential for industrial applications, typically exhibit only a fraction of the performance promised by the high mobility results achieved in laboratory research on longer channel lengths (a few tens of mu m or even longer). In this paper, we present results demonstrating solution processed devices having width-normalised contact resistances of less than 300 Ohm cm and show how these can be made into 5-stage ring oscillator circuits with the highest frequency of 1.08 MHz, corresponding to a stage delay of 93 ns. This is achieved through use of a thin, uniform high performance organic semiconductor (OSC) film made possible through formulation of a small-molecule semiconductor in a high-k binder polymer. The OSC formulation is employed in a fabrication process compatible with mass manufacture, opening up the route to commercial products made from organic thin-film transistor (OTFT) devices with high performance.