Recent advances in the orientation of conjugated polymers for organic field-effect transistors

Solution processable conjugated polymers (CPs) possess unique molecular structures in terms of extended π-conjugation in combination with quasi 1-dimensionality, imparting them with an inherent tendency for molecular self-assembly and ultimately determining their optoelectronic properties. Short-range molecular ordering and long-range macroscopic orientation are two different but interdependent phenomena, which should be optimized depending on the nature of electronic devices (planar versus vertical). Judicious control of the macromolecular orientations and conformation-assisted morphologies of CPs are key for determining and controlling the anisotropic charge transport in organic field effect transistors (OFETs). The present review focuses on different solution-based approaches for thin film fabrication developed in the last two decades aimed towards controlling the film morphologies and macroscopic orientations of CPs. It summarizes the information for understanding the various techniques utilized for controlling the molecular ordering and macroscopic orientation in CP thin films in order to correlate device performance and anisotropic charge transport in OFETs. Systematic organization of topics and critical analysis of progress and improvisations are included, along with current state-of-the-art approaches for each technique being discussed in detail. Apart from commentary on the pros and cons of various techniques, this review summarizes the future directions necessary for further development in the area of next-generation flexible electronics. This review summarizes recent advancements in various orientation techniques for conjugated polymers for use in high performance organic field effect transistors.