Facile and Fine Polarity-Tuning of Polymeric Semiconductors: The Effects of Nitrile Groups on Polymer-Polymer Blend Systems

Abstract

Currently, the majority of high performance ambipolar polymer field effect transistors rely on the synthesis of donor-acceptor conjugated polymers with balanced hole/electron mobilities, whose polarity is predetermined during synthesis. However, further tuning of the device polarity is necessary in many applications, and a facile and fine polarity tuning with additional fabrication steps is necessary. To solve these issues, the utilization of polymer-polymer blends is recommended in which the electronic configuration and charge transport characteristics can be finely rationalized. A polymer-polymer blend system consisting of two different donor-acceptor polymeric semiconductors, namely PDPPTVT and PDPPCNTVT, is introduced with nearly identical chemical structures apart from the presence of a nitrile group. The nitrile group in PDPPCNTVT creates some important differences in terms of molecular orientation and surface energy in comparison to PDPPTVT. However, because of the chemical similarity, blend films consisting of these two polymers show outstanding homogeneous morphologies, enabling a facile and fine polarity tuning to be realized simply by changing the mixture ratio. A 1: 1 blend ratio between PDPPTVT with hole mobility of approximate to 1 cm(2) V-1 s(-1) and PDPPCNTVT with electron mobility of approximate to 1 cm(2) V-1 s(-1) enables an almost balanced charge carrier mobility of approximate to 0.5 cm(2) V-1 s(-1) for both holes and electrons.