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Orientation Control of Linear-Shaped Molecules in Vacuum-Deposited Organic Amorphous Films and Its Effect on Carrier Mobilities

Authors

  • Daisuke Yokoyama,

    Corresponding author
    1. Center for Future Chemistry Kyushu University 774 Motooka, Nishi, Fukuoka 819-0395 (Japan)
    2. BEANS Laboratory 67 Kandasakumakashi, Chiyoda, Tokyo 101-0026 (Japan)
    3. Current address: Graduate School of Science and Engineering, Yamagata University, 4-3-16 Johnan, Yonezawa, Yamagata 992-8510 (Japan)
    • Center for Future Chemistry Kyushu University 774 Motooka, Nishi, Fukuoka 819-0395 (Japan)
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  • Yousuke Setoguchi,

    1. Center for Future Chemistry Kyushu University 774 Motooka, Nishi, Fukuoka 819-0395 (Japan)
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  • Akio Sakaguchi,

    1. J. A. Woollam Japan Corporation 5-22-9 Ogikubo, Suginami, Tokyo 167-0051 (Japan)
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  • Michio Suzuki,

    1. J. A. Woollam Japan Corporation 5-22-9 Ogikubo, Suginami, Tokyo 167-0051 (Japan)
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  • Chihaya Adachi

    Corresponding author
    1. Center for Future Chemistry Kyushu University 774 Motooka, Nishi, Fukuoka 819-0395 (Japan)
    2. BEANS Laboratory 67 Kandasakumakashi, Chiyoda, Tokyo 101-0026 (Japan)
    • Center for Future Chemistry Kyushu University 774 Motooka, Nishi, Fukuoka 819-0395 (Japan)
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Abstract

The molecular orientation of linear-shaped molecules in organic amorphous films is demonstrated to be controllable by the substrate temperature. It is also shown that the molecular orientation affects the charge-transport characteristics of the films. Although linear-shaped 4,4′-bis[(N-carbazole)styryl]biphenyl molecules deposited on substrates at room temperature are horizontally oriented in amorphous films, their orientation when deposited on heated substrates with smooth surfaces becomes more random as the substrate temperature increases, even at temperatures under the glass transition temperature. Another factor dominating the orientation of the molecules deposited on heated substrates is the surface roughness of the substrate. Lower carrier mobilities are observed in films composed of randomly oriented molecules, demonstrating the significant effect of a horizontal molecular orientation on the charge-transport characteristics of organic amorphous films.

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