The Impact of Interfacial Mixing on Förster Transfer at Conjugated Polymer Heterojunctions

Authors

  • Anthony M. Higgins,

    Corresponding author
    1. Multidisciplinary Nanotechnology Centre School of Engineering, Swansea University Singleton Park, Swansea, SA2 8PP (UK)
    • Multidisciplinary Nanotechnology Centre School of Engineering, Swansea University Singleton Park, Swansea, SA2 8PP (UK).
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  • Ashley Cadby,

    1. Department of Physics and Astronomy University of Sheffield, Hicks Building Hounsfield Road, Sheffield, S3 7RH (UK)
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  • David G. Lidzey,

    1. Department of Physics and Astronomy University of Sheffield, Hicks Building Hounsfield Road, Sheffield, S3 7RH (UK)
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  • Robert M. Dalgliesh,

    1. ISIS, Rutherford Appleton Laboratory Didcot, OX11 0QX (UK)
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  • Mark Geoghegan,

    1. Department of Physics and Astronomy University of Sheffield, Hicks Building Hounsfield Road, Sheffield, S3 7RH (UK)
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  • Richard A. L. Jones,

    1. Department of Physics and Astronomy University of Sheffield, Hicks Building Hounsfield Road, Sheffield, S3 7RH (UK)
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  • Simon J. Martin,

    1. Department of Physics and Astronomy University of Sheffield, Hicks Building Hounsfield Road, Sheffield, S3 7RH (UK)
    2. Present address: Institute of Polymer Technology and Materials Engineering (IPTME), Loughborough University, Loughborough LE11 3TU, (UK)
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  • Sasha Y. Heriot

    1. Department of Physics and Astronomy University of Sheffield, Hicks Building Hounsfield Road, Sheffield, S3 7RH (UK)
    2. Present address: Chamelic Ltd. Leeds Innovation Centre, 103 Clarendon Road, Leeds LS2 9DF (UK)
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Abstract

Neutron reflectivity and photoluminescence measurements are reported on bilayers of polyfluorene-based conjugated polymers. By using a novel thermal processing procedure it is possible to control the width of the interface between poly(9,9-dioctylfluorene) (F8) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT), and measure the impact of interfacial roughness on the resonant energy transfer of excitons at the interface (Förster transfer). It is found that increasing the root mean square (rms) roughness of the F8/F8BT interface over the range of ∼1 nm to ∼5 nm leads to a greatly enhanced Förster transfer from F8 to F8BT molecules. By comparing photoluminescence measurements with simple calculations it is concluded that the level of enhancement of the F8BT peak at rough interfaces can only be adequately explained if mixing of F8 and F8BT at a molecular level dominates over the interfacial roughness due to thermally excited capillary waves.

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