Cover Picture: n-Channel, Ambipolar, and p-Channel Organic Heterojunction Transistors Fabricated with Various Film Morphologies (Adv. Funct. Mater. 3/2007)

Authors

  • J. W. Shi,

    1. State Key Laboratory of Polymer Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
    2. Graduate School of Chinese Academy of Sciences, Beijing 100039, P.R. China
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  • H. B. Wang,

    1. State Key Laboratory of Polymer Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
    2. Graduate School of Chinese Academy of Sciences, Beijing 100039, P.R. China
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  • D. Song,

    1. State Key Laboratory of Polymer Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
    2. Graduate School of Chinese Academy of Sciences, Beijing 100039, P.R. China
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  • H. K. Tian,

    1. State Key Laboratory of Polymer Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
    2. Graduate School of Chinese Academy of Sciences, Beijing 100039, P.R. China
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  • Y. H. Geng,

    1. State Key Laboratory of Polymer Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
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  • D. H. Yan

    1. State Key Laboratory of Polymer Chemistry and Physics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P.R. China
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Abstract

Simultaneous introduction of short-range repulsive interactions between dissimilar colloidal particles and attractive interactions between like particles provides a general new route to fabricating self-organizing bipolar devices. By identifying combinations of conductive device materials between which short-range repulsive forces exist in the presence of an intervening liquid, electrochemical junctions can be self-formed, as reported by Chiang and co-workers on p. 379.

The relationship between the performance characteristics of organic field-effect transistors (OFETs) with 2,5-bis(4-biphenylyl)bithiophene/copper hexadecafluorophthalocyanine (BP2T/F16CuPc) heterojunctions and the thickness of the BP2T bottom layer is investigated. Three operating modes (n-channel, ambipolar, and p-channel) are obtained by varying the thickness of the organic semiconductor layer. The changes in operating mode are attributable to the morphology of the film and the heterojunction effect, which also leads to an evolution of the field-effect mobility with increasing film thickness. In BP2T/F16CuPc heterojunctions the mobile charge carriers accumulate at both sides of the heterojunction interface, with an accumulation layer thickness of ca. 10 nm. High field-effect mobility values can be achieved in continuous and flat films that exhibit the heterojunction effect.

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