Issue 89, 2017

Thermally induced bilayered crystals in a solution-processed polycrystalline thin film of phenylterthiophene-based monoalkyl smectic liquid crystals and their effect on FET mobility

Abstract

Herein, a series of asymmetric monoalkyl terthiophene derivatives, 5-phenyl-5′′-alkyl-2,2′:5′,2′′-terthiophene (Ph-(Tp)3-Cn, 6 ≤ n ≤ 18, where n represents the number of carbons in the alkyl group), were synthesized to investigate the formation of monolayered crystals derived from the smectic phase and their phase transition to bilayered crystals, leading to a significant increase of FET mobility when applied to organic field-effect transistors. All compounds showed a highly ordered smectic phase, i.e., SmE phase, and gave a monolayered crystal when spin-coated at SmE temperature. It was found that phase transition from monolayered to bilayered crystals was induced by thermal annealing when the alkyl side chain length n ≥ 10, and OFET mobility in FETs fabricated with polycrystalline thin films was dramatically enhanced up to one order of magnitude when the bilayered crystals were formed. This result proves that this phase transition is not limited to a particular type of smectic liquid crystals consisting of an aromatic fused ring system reported in benzothienobenzothiphene (BTBT) as a core derivative and can be extended to a variety of core systems, e.g., oligomer type of smectic liquid crystals. These findings may provide a new strategy for molecular design to boost mobility in soluble OFET materials.

Graphical abstract: Thermally induced bilayered crystals in a solution-processed polycrystalline thin film of phenylterthiophene-based monoalkyl smectic liquid crystals and their effect on FET mobility

Supplementary files

Article information

Article type
Paper
Submitted
24 Oct 2017
Accepted
02 Dec 2017
First published
15 Dec 2017
This article is Open Access
Creative Commons BY license

RSC Adv., 2017,7, 56586-56593

Thermally induced bilayered crystals in a solution-processed polycrystalline thin film of phenylterthiophene-based monoalkyl smectic liquid crystals and their effect on FET mobility

H. Wu, H. Iino and J. Hanna, RSC Adv., 2017, 7, 56586 DOI: 10.1039/C7RA11727B

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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