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Proceedings Paper

Using mesophase morphology to improve charge transport properties in liquid crystal semiconductors (Conference Presentation)
Author(s): Eric Carlson; Dayan Wei; Lee Foley; David Walba
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Paper Abstract

Organic semiconductors show promise in the development of a new age of electronics that are inexpensive, flexible, wearable, and bio-compatable. A great amount of work has been done to engineer and characterize new organic semiconductors in organic thin film transistors (OTFTs), resulting in charge carrier mobility values greater than 10cm2/Vs. The performances of these devices still fall well short of their silicon counterparts mostly due to molecular morphology, grain size, and carrier concentration. One solution to these problems is to use the intrinsic order found in liquid crystal (LC) mesophases. Previous work shows that [1]benzothieno[3,2-b][1]benzothiophene (BTBT) can be used to produce high-performing OFTFs. This is due large in part to the paramorphic SmE to crystal transition commonly seen in these materials that induces long-range molecular order within the crystal structure. In this work, we synthesized and characterized single-tailed BTBT molecules that contain a paramorphic SmE to crystal transition in single-step solution-processed OTFTs. Further, the addition of a pentafluorobenzene thiol (PFBT) self-assembled monolayer (SAM) to the gold electrodes improved charge injection, reducing the device threshold voltage and increasing the on/off ratio. It is suspected that the molecular packing is responsible for high mobility values. Future work will aim to explore the use of host-guest chemistry doping and LC alignment techniques to further improve carrier concentration and charge transfer properties to improve bulk material transport properties.

Paper Details

Date Published: 18 September 2018
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Proc. SPIE 10735, Liquid Crystals XXII, 107350X (18 September 2018); doi: 10.1117/12.2320712
Show Author Affiliations
Eric Carlson, Univ. of Colorado Boulder (United States)
Dayan Wei, Univ. of Colorado Boulder (United States)
Lee Foley, Univ. of Colorado Boulder (United States)
David Walba, Univ. of Colorado Boulder (United States)


Published in SPIE Proceedings Vol. 10735:
Liquid Crystals XXII
Iam Choon Khoo, Editor(s)

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