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Time-resolved electrostatic force microscopy of polymer solar cells

Nature Materials volume 5, pages 735–740 (2006)Cite this article

Abstract

Blends of conjugated polymers with fullerenes, polymers, or nanocrystals make promising materials for low-cost photovoltaic applications. Different processing conditions affect the efficiencies of these solar cells by creating a variety of nanostructured morphologies, however, the relationship between film structure and device efficiency is not fully understood. We introduce time-resolved electrostatic force microscopy (EFM) as a means to measure photoexcited charge in polymer films with a resolution of 100 nm and 100 μs. These EFM measurements correlate well with the external quantum efficiencies measured for a series of polymer photodiodes, providing a direct link between local morphology, local optoelectronic properties and device performance. The data show that the domain centres account for the majority of the photoinduced charge collected in polyfluorene blend devices. These results underscore the importance of controlling not only the length scale of phase separation, but also the composition of the domains when optimizing nanostructured solar cells.

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Figure 1: Measuring photoexcited charge with an AFM.
Figure 2: Time-resolving charge creation.
Figure 3: Charging rate image of a polymer blend film.
Figure 4: Correlating charging rate and EQE.

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Acknowledgements

We thank O. Reid and Y. Chen for their experimental assistance, Asylum Research for their continuing help, M. Chiesa and R. Shikler for their comments on the manuscript and H. Snaith for his comments and for valuable discussions. This material is based on work supported by the National Science Foundation (DMR 0449422) and the STC Program of the National Science Foundation (DMR 0120967).

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  1. Department of Physics, University of Washington, Seattle, Washington, 98195-1560, USA

    David C. Coffey

  2. Department of Chemistry, University of Washington, Seattle, Washington, 98195-1700, USA

    David S. Ginger

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Correspondence to David S. Ginger.

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Coffey, D., Ginger, D. Time-resolved electrostatic force microscopy of polymer solar cells. Nature Mater 5, 735–740 (2006). https://doi.org/10.1038/nmat1712

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