Corona Poling Induced Phase Transition to Highly Polar Phase in P(VDF-TrFE-CFE) Dielectric and Charge Transport of Organic Field-Effect Transistors.

Abstract

Increasing the number of charge carriers flowing through the charge transport channel to improve the electrical performance of organic field-effect transistors (OFETs) is important because it leads to a low driving voltage and a high drain current value. This paper proposes a new strategy, the corona poling process, to enhance the electrical performance of OFETs using an external electric field when forming a dielectric film using a PVDF-based high-k dielectric terpolymer, P(VDF-TrFE-CFE). A corona poling process was applied to align the dipoles with high-k dielectric molecules and improve the capacitance, thereby increasing the number of charge carriers. Through this process, by observing the phase transition of a PVDF dielectric through a corona poling process in the GIWAXS data, the phase transition through an external electric field was thoroughly revealed for the first time. As a result, the capacitance of high-k dielectric films can be improved, and the amount of charge carriers can be increased by a simple corona poling process. In addition, to reduce the effect of deep trap sites caused by the dipole alignment, a thin low-k dielectric, polystyrene (PS), was introduced between the active and high-k dielectric layers to provide trap site passivation, thereby increasing the electrical performance of the OFET. Therefore, through this strategy, using a diketopyrrolopyrrole (DPP)-based donor-acceptor (D-A) copolymer as an active material of OFET, the average saturation region hole mobility was improved from 0.34 to 0.60 cm2/Vs. Thus, the electrical performances of the OFETs were improved by enhancing the capacitance through the corona poling process and reducing the charge carrier trap sites introduced by the high-k and low-k bi-layer dielectric layer. Importantly, this work offers a new strategy for the post-treatment to improve electrical performance of organic devices.