Manipulating Transistor Operation via Nonuniformly Distributed Charges in a Polymer Insulating Electret Layer

Organic field-effect transistors (FETs) with high-field-effect mobility (μFET) and on:off ratio are attractive for flexible electronics. In this paper, we propose a design principle for manipulating transistor operations to in situ improve both the μFET and on:off ratio of polymer transistors using nonuniformly distributed charges along an insulator electret layer between semiconductor and dielectric layers. Such nonuniform electrets obtained via applying gate-voltage stress with specific source-drain voltages provide a nonuniform electric field across the semiconductor layer and, thus, serve as a "nonuniform floating gate". As compared with transistors without electrets or with uniform electrets, nonuniform electrets lead to a different device operation; therefore, a much narrower gate-voltage range can be sufficient to switch the transistor between the on and off states representing a higher switching speed. The apparent μFET of poly(3-hexylthiophene) semiconductor film is significantly improved by 1 order to higher than 1 cm2 V-1 s-1, with simultaneously improving the on:off ratio up to 108.