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Structural and Electronic Origin of Bis-Lactam-Based High-Performance Organic Thin-Film Transistors

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journal contribution
posted on 30.01.2019, 00:00 by Jin Hong Kim, Min-Woo Choi, Won Sik Yoon, Sangyoon Oh, Seung Hwa Hong, Soo Young Park
We describe herein the comprehensive theoretical and experimental studies on the transistor mobility of organic semiconductors by correlating a two-dimensional (2D) intermolecular interaction with thin-film morphology and the electronic coupling structure. We developed a novel bis-lactam-based small molecule, 1,5-dioctyl-3,7-di­(thiophen-2-yl)-1,5-naphthyridine-2,6-dione (C8-NTDT), with a 2D-type C–H···OC intermolecular interaction along the in-plane directions of the crystal packing structure, which is characteristically different from the one-dimensional-type intermolecular interaction shown in the typical bis-lactam molecule of 2,5-dioctyl-3,6-di­(thiophen-2-yl)­pyrrolo­[3,4-c]­pyrrole-1,4-dione (C8-DPPT). Experimentally and theoretically, C8-NTDT exhibited more favorable thin-film morphology and an electronic coupling structure for charge transport because of its unique 2D intermolecular interactions compared with C8-DPPT. In fact, C8-NTDT exhibited a hole mobility of up to 1.29 cm2 V–1 s–1 and an on/off ratio of 107 in a vacuum-processed device. Moreover, the high solubility with the 2D electronic coupling structure of C8-NTDT enables versatile solution processing for device fabrication without performance degradation compared to the vacuum-processed device. As an example, we could demonstrate a hole mobility of up to 1.10 cm2 V–1 s–1 for the spin-coated devices, which is one of the best performances among the solution-processed organic field-effect transistors based on bis-lactam-containing small molecules.

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