Efficient Phthalimide Copolymer-Based Bulk Heterojunction Solar Cells: How the Processing Additive Influences Nanoscale Morphology and Photovoltaic Properties

Authors

  • Hao Xin,

    1. Department of Chemical Engineering and Department of Chemistry, University of Washington, Box 351750, Seattle, Washington 98195-1750, USA
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  • Xugang Guo,

    1. Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
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  • Guoqiang Ren,

    1. Department of Chemical Engineering and Department of Chemistry, University of Washington, Box 351750, Seattle, Washington 98195-1750, USA
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  • Mark D. Watson,

    Corresponding author
    1. Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
    • Department of Chemistry, University of Kentucky, Lexington, Kentucky 40506-0055, USA
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  • Samson A. Jenekhe

    Corresponding author
    1. Department of Chemical Engineering and Department of Chemistry, University of Washington, Box 351750, Seattle, Washington 98195-1750, USA
    • Department of Chemical Engineering and Department of Chemistry, University of Washington, Box 351750, Seattle, Washington 98195-1750, USA.
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Abstract

The power conversion efficiency of poly(N-(2-ethylhexyl)-3,6-bis(4-dodecyloxythiophen-2-yl)phthalimide) (PhBTEH)/fullerene bulk heterojunction solar cells improves from 0.43 to 4.1% by using a processing additive. The underlying mechanism for the almost 10-fold enhancement in solar cell performance is found to be inhibition of fullerene intercalation into the polymer side chains and regulation of the relative crystallization/aggregation rates of the polymer and fullerene. An optimal interconnected two-phase morphology with 15–20 nm domains is obtained when a processing additive is used compared with 100–300 nm domains without the additive. The results demonstrate that a processing additive provides an effective means of controlling both the fullerene intercalation in polymer/fullerene blends and the domain sizes of their phase-separated nanoscale morphology.

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