Uniaxial Alignment of Conjugated Polymer Films for High‐Performance Organic Field‐Effect Transistors

• Published in: Advanced materials (Weinheim) Vol. 30; no. 20; pp. e1705463 - n/a
• Main Authors: Khim, Dongyoon, Luzio, Alessandro, Bonacchini, Giorgio Ernesto, Pace, Giuseppina, Lee, Mi‐Jung, Noh, Yong‐Young, Caironi, Mario
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.05.2018
• Subjects: aligned polymer films; Alignment; Carrier mobility; Current carriers; Electronic devices; Molecular chains; Optoelectronics; organic field‐effect transistors; Polymer films; polymer semiconductors; Polymers; Portable equipment; printed electronics; Semiconductor devices; Thin films; Transistors; transport anisotropy; Transport properties; Weight reduction; polymer semiconductors; printed electronics; aligned polymer films; organic field-effect transistors; transport anisotropy
• DOI: 10.1002/adma.201705463
• ISSN: 0935-9648; 1521-4095

Polymer semiconductors have been experiencing a remarkable improvement in electronic and optoelectronic properties, which are largely related to the recent development of a vast library of high‐performance, donor–acceptor copolymers showing alternation of chemical moieties with different electronic affinities along their backbones. Such steady improvement is making conjugated polymers even more appealing for large‐area and flexible electronic applications, from distributed and portable electronics to healthcare devices, where cost‐effective manufacturing, light weight, and ease of integration represent key benefits. Recently, a strong boost to charge carrier mobility in polymer‐based field‐effect transistors, consistently achieving the range from 1.0 to 10 cm2 V−1 s−1 for both holes and electrons, has been given by uniaxial backbone alignment of polymers in thin films, inducing strong transport anisotropy and favoring enhanced transport properties along the alignment direction. Herein, an overview on this topic is provided with a focus on the processing–structure–property relationships that enable the controlled and uniform alignment of polymer films over large areas with scalable processes. The key aspects are specific molecular structures, such as planarized backbones with a reduced degree of conformational disorder, solution formulation with controlled aggregation, and deposition techniques inducing suitable directional flow. Uniaxial alignment represents a key factor to boost the charge mobility in polymer‐based field‐effect transistors. The subject is critically reviewed, collecting all recent approaches to the alignment of polymer semiconductors, and covering all aspects of solution formulations, control of solid‐state packing, and integration into electronic devices.