Sub-threshold charge transport in polymer transistors

Research on polymer transistors has taken center stage due to their promise for use in displays, large-area electronics, and sensors. Most transistors with disordered semiconductor active layers such as amorphous silicon and polymers, have a large density of bulk trap states. Sub-threshold conduction in such transistors is very important. In particular, charge transport in the drift-limited sub-threshold regime is important and has not been adequately investigated. In this work, we will present an analysis of sub-threshold charge transport in polymer transistors with active layers based on the diketopyrrolopyrrole (DPP) core. Such transistors possess room temperature field-effect mobilities of over 2 cm$^{\mathrm{2}}$/Vs. We present an analysis of both above threshold and below threshold charge transport and show how the transport mechanisms change with temperature and charge density. We will also discuss a method to correctly calculate the density of trap states by sub-threshold modeling.