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 throughthe chargetransport channel to improve the electrical performance of organicfield-effect transistors (OFETs) is important because it leads toa low driving voltage and a high drain current value. This paper proposesa new strategy, the corona poling process, to enhance the electricalperformance of OFETs using an external electric field when forminga dielectric film using a PVDF-based high-k dielectric terpolymer,P(VDF-TrFE-CFE). A corona poling process was applied to align thedipoles 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 coronapoling process in the GIWAXS data, the phase transition through anexternal 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 coronapoling process. In addition, to reduce the effect of deep trap sitescaused by the dipole alignment, a thin low-k dielectric, polystyrene(PS), was introduced between the active and high-k dielectric layersto provide trap site passivation, thereby increasing the electricalperformance of the OFET. Therefore, through this strategy, using adiketopyrrolopyrrole (DPP)-based donor-acceptor (D-A)copolymer as an active material of OFET, the average saturation regionhole mobility was improved from 0.34 to 0.60 cm(2)/Vs. Thus,the electrical performances of the OFETs were improved by enhancingthe capacitance through the corona poling process and reducing thecharge carrier trap sites introduced by the high-k and low-k bi-layerdielectric layer. Importantly, this work offers a new strategy forthe post-treatment to improve electrical performance of organic devices.