Issue 47, 2007
From the journal:

Journal of Materials Chemistry

Highly ordered thin films of a bis(dithienothiophene) derivative

Christoph Hunziker,*a   Xiaowei Zhan,*bc   Paolo A. Losio,a   Harry Figi,a   O-Pil Kwon,a   Stephen Barlow,b   Peter Güntera  and  Seth R. Marder*b  

* Corresponding authors

a Institute of Quantum Electronics, Nonlinear Optics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland
E-mail: christoph.hunziker@phys.ethz.ch

b School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
E-mail: seth.marder@chemistry.gatech.edu

c Beijing National Laboratory for Molecular Sciences and Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China
E-mail: xwzhan@iccas.ac.cn

Abstract

We report growth as well as structural, optical, and charge-transport properties of highly ordered thin films of a fused thiophene derivative, 6,6′-di-n-hexyl-[2,2′]bi(dithieno[3,2-b:2′,3′-d]thiophenyl) (DH-BDT). DH-BDT was synthesised with the aim of fabricating high quality, molecularly aligned thin films for organic electronic applications. Structural phase transitions are observed upon heating from room temperature, indicating the existence of three different polymorphs, denoted α, β and γ. The transition temperatures are Tα→β = 92 ± 2 °C and Tβ→γ = 140 ± 2 °C. The growth of thin films of DH-BDT can be controlled to afford either the β- or the γ-phase. Thermal annealing leads to the formation of large single crystalline grains with areas as large as 7 × 104 μm2. The molecules in the γ-phase are cofacially aligned and show horizontally layered thin film growth. The good crystallinity and the large grain size in the γ-phase lead to hole mobilities up to μγ = 0.09 cm2 V−1 s−1, based on the measurement of space-charge-limited currents (SCLC). The β-phase consists of mutually shifted molecules, resulting in a lower hole mobility of 4.4 × 10−5 cm2 V−1 s−1 but improving the relative luminescence quantum yield by 140% relative to that of the γ-phase. Field-effect transistors of DH-BDT in the γ-phase have been fabricated and yield hole mobilities which are of the same order of magnitude as the SCLC mobilities.

Graphical abstract: Highly ordered thin films of a bis(dithienothiophene) derivative

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Article information

DOI
https://doi.org/10.1039/B711483D
Article type
Paper
Submitted
26 Jul 2007
Accepted
27 Sep 2007
First published
16 Oct 2007

J. Mater. Chem., 2007,17, 4972-4979

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Highly ordered thin films of a bis(dithienothiophene) derivative

C. Hunziker, X. Zhan, P. A. Losio, H. Figi, O. Kwon, S. Barlow, P. Günter and S. R. Marder, J. Mater. Chem., 2007, 17, 4972 DOI: 10.1039/B711483D

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