Tuning the threshold voltage of organic field-effect transistors by an electret encapsulating layer

Here, the authors present a technique to adjust the threshold voltage of an organic field-effect transistor (OFET) using a design similar to a dual-gate structure with an insulating Teflon-based electret layer as a second gate. The threshold voltage of a pentacene bottom gate OFET was shifted from +13.1 to -2.3 V by depositon of a 1.7 mu m thick electret layer, proving the principal feasibility of this approach. This controlled tuning of the threshold voltage compensates one of the main drawbacks of organic electronics and even allows switching from a depletion to an enhancement-type transistor behavior.