Organic thin films with charge-carrier mobility exceeding that of single crystalsElectronic supplementary information (ESI) available: Electronic band structures and densities of states as calculated by DFT, illustration of dominant charge transport pathways, GID maps of single crystals and thin films. See DOI: 10.1039/c7tc03324a

• Main Authors: Lamport, Zachary A, Li, Ruipeng, Wang, Chao, Mitchell, William, Sparrowe, David, Smilgies, Detlef-M, Day, Cynthia, Coropceanu, Veaceslav, Jurchescu, Oana D
• Format: Journal Article
• Language: English
• Published: 12.10.2017
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c7tc03324a

The performance of organic field-effect transistors (OFETs) depends heavily upon the intrinsic properties and microstructure of the semiconducting layer, the processes taking place at the semiconductor/dielectric interface, and the quality of contacts. In this article, we report on 7,14-bis(trimethylsilylethynyl) benzo[ k ]tetraphene single crystal and thin-film OFETs and compare their properties. We find that the single crystals exhibit a pronounced anisotropy in electrical characteristics, with a maximum field-effect mobility of 0.3 cm 2 V −1 s −1 . Through density functional theory (DFT) calculations we identified the main direction for hole transport, which was confirmed by X-ray diffraction (XRD) measurements as parallel to the plane of the single crystal facet where the transport was probed. By processing the material as a thin-film semiconductor, the content of high-mobility direction probed within the transistor channel was enhanced. The control of film morphology, coupled with a different design of the device structure allowed us to obtain an order of magnitude higher charge-carrier mobilities and a very small spread in device performance. Through processing, spin-cast OTFTs outperform single-crystal OFETs by making accessible the high-mobility direction in the same crystal structure.