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H-Aggregation Strategy in the Design of Molecular Semiconductors for Highly Reliable Organic Thin Film Transistors

Authors

  • Seul-ong Kim,

    1. School of Materials Science and Engineering, Engineering Research Institute, Gyeongsang National University, Jinju 660–701, Korea
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  • Tae Kyu An,

    1. Polymer Research Institute, Department of Chemical Engineering, Pohang University of Science Technology, Pohang 790–784, South Korea
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  • Jun Chen,

    1. School of Materials Science and Engineering, Engineering Research Institute, Gyeongsang National University, Jinju 660–701, Korea
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  • Il Kang,

    1. School of Materials Science and Engineering, Engineering Research Institute, Gyeongsang National University, Jinju 660–701, Korea
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  • So Hee Kang,

    1. Department of Chemistry, Gyeongsang National University JinJu, 600–701, Korea
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  • Dae Sung Chung,

    1. Polymer Research Institute, Department of Chemical Engineering, Pohang University of Science Technology, Pohang 790–784, South Korea
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  • Chan Eon Park,

    Corresponding author
    1. Polymer Research Institute, Department of Chemical Engineering, Pohang University of Science Technology, Pohang 790–784, South Korea
    • Polymer Research Institute, Department of Chemical Engineering, Pohang University of Science Technology, Pohang 790–784, South Korea.
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  • Yun-Hi Kim,

    Corresponding author
    1. Department of Chemistry, Gyeongsang National University JinJu, 600–701, Korea
    • Department of Chemistry, Gyeongsang National University JinJu, 600–701, Korea
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  • Soon-Ki Kwon

    Corresponding author
    1. School of Materials Science and Engineering, Engineering Research Institute, Gyeongsang National University, Jinju 660–701, Korea
    • School of Materials Science and Engineering, Engineering Research Institute, Gyeongsang National University, Jinju 660–701, Korea
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Abstract

Four new quaterthiophene derivatives with end-groups composed of dicyclohexyl ethyl (DCE4T), dicyclohexyl butyl (DCB4T), cyclohexyl ethyl (CE4T), and cyclohexyl butyl (CB4T) were designed. All materials showed high solubility in common organic solvents. UV–vis absorption measurements showed that the quaterthiophene derivatives with asymmetrically substituted cyclohexyl end-groups (CE4T and CB4T) preferred H-type aggregation whereas those with symmetrically substituted cyclohexyl end-groups (DCE4T and DCB4T) preferred J-type aggregation. The molecular structure-dependent packing (H or J) of the new quaterthiophene derivatives was analyzed by grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements. The field-effect mobilities of devices that incorporated the asymmetrical molecules, CE4T and CB4T, were quite high, above 10−2 cm2 V−1 s−1, due to H-aggregation, whereas the field-effect mobilities of devices that incorporated symmetrical molecules, DCE4T and DCB4T, were poor, below 10−4 cm2 V−1 s−1, due to J-aggregation. More importantly, H-aggregation within the thin film provided stable crystalline morphologies in the spin-coated films, and, thus, thin film transistors (TFTs) using cyclohexylated quaterthiophenes yielded highly reproducible transistor performances. The distributions of measured field-effect mobilities in transistors based on cyclohexylated quaterthiophenes with H-aggregation were remarkably narrow.

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