Template-Assisted Fabrication of Single-Crystal-Like Polymer Fibers for Efficient Charge Transport

Polymer semiconductors with highly crystalline forms, such as crystalline nanowires and fibers, are critical for charge carrier transport in organic field-effect transistors (OFET). However, the highly crystalline form usually requires high-quality molecular orderliness, which still remains a great challenge, especially in single fibers of extremely high-molecular-weight semiconducting polymers. In this study, we present an anodic aluminum oxide (AAO) template-assisted method to fabricate highly crystalline N-alkyl diketopyrrolopyrrole dithienylthieno[3,2-b]thiophene (DPP-DTT) single fibers. Grazing-incidence X-ray diffraction and selected area electron diffraction show obvious diffraction patterns for single-crystal-like characteristics, indicating the highly ordered molecular chains and highly crystalline structures of the single DPP-DTT fibers. OFET based on the single-crystal-like DPP-DTT fiber exhibits the highest charge carrier mobility of up to 14.2 cm2 V-1 s-1 and an average mobility of approximately 7.8 cm2 V-1 s-1, which is significantly improved compared with DPP-DTT thin film-based devices. Besides, the fiber-based OFET also exhibit a high light responsivity of 4.0 x 103 A W-1. This work demonstrates a facile and effective method for fabricating single-crystal-like fibers of high-molecular-weight polymer semiconductors and corresponding high-performance OFET devices. Furthermore, it also expands application of AAO template method for achieving crystalline semiconducting polymer fibers and provide a new perspective for the study on polymer crystallization.