Collaborative Morphological and Electrical Regulation of High-Mobility Conjugated Polymers via a Multifunctional Polymeric Additive

Abstract

Morphological and electrical control over conjugated polymers has a great potential for the fabrication of high-performance organic thin-film transistors (OTFTs). Herein, we employed a multifunctional polymeric additive, namely, PBTTT-b-HTPB, to optimize the molecular packing order of an isoindigo-based model polymer (IIDSiC8) and simultaneously regulate the minority carriers for boosted transport properties in OTFTs via facile solution processing. By detailed comparative study, we demonstrated that PBTTT-b-HTPB remarkably improved the crystallinity of IIDSiC8 by forming elongated fibers with higher molecular order in a thin film, which originated from the larger size ordered solution aggregates due to the presence of the insulating block. On the other hand, the p-type conjugated block of PBTTT worked as a hole trapping center, resulting in significantly increased electron density, reduced off-current, and optimal n-type performance. Benefiting from the collaborative morphological and electrical regulation, IIDSiC8/PBTTT-b-HTPB films displayed well-aligned ordered morphology and a high electron mobility up close to 7 cm² V^–1 s^–1 together with an on/off ratio of 10⁶ in bar-coated OTFTs. The high electron mobility is among the top performance values reported for isoindigo-based polymers. Our work has achieved simultaneous optimization of film microstructures and carrier transport characteristics of polymer semiconductors, providing opportunities for the production of OTFT devices with a superior performance.