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Streamlined microwave-assisted preparation of narrow-bandgap conjugated polymers for high-performance bulk heterojunction solar cells

Nature Chemistry volume 1, pages 657–661 (2009)Cite this article

Abstract

The most efficient plastic solar cells comprise a blend of conjugated polymer and a suitable electron acceptor, typically a fullerene derivative. Therefore narrow-bandgap conjugated polymers are currently sought for the fabrication of such devices. A significant challenge is being able to predict device function and performance from consideration of the molecular connectivity and dimensions of the partners within the active layer. Improved chemical syntheses are therefore required to make structurally varied polymers and enable the delineation of structure–function relationships with the aim of improving power conversion efficiencies. Here, we demonstrate that microwave heating in combination with the screening of comonomer reactant ratios can be used to obtain donor–acceptor copolymers with high average molecular weights and properties that make them suitable for solar cell incorporation. Furthermore, we highlight the importance of high molecular weight and the contribution of solubilizing side groups in determining the final device properties.

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Figure 1: The molecular structures and syntheses of P1, P2 and PCPDTBT.
Figure 2: The UV–vis absorption spectra of P1, P2 and PCPDTBT prepared via microwave irradiation.
Figure 3: Selected area electron diffraction (SAED) patterns can be used to evaluate the internal order of the polymer films.
Figure 4: The solar cell characteristics of bulk heterojunction devices prepared from P1 or P2 and PC71BM.
Figure 5: The current density–voltage characteristics of P2:PC71BM solar cells as a function of number average molecular weight (Mn).

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Acknowledgements

The research was supported by grants from the Department of Energy, the Institute for Collaborative Biotechnologies and the Air Force Office of Scientific Research.

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Authors and Affiliations

  1. Departments of Chemistry & Biochemistry and Materials, Center for Polymers and Organic Solids, University of California, Santa Barbara, California, USA

    Robert C. Coffin, Jeff Peet, James Rogers & Guillermo C. Bazan

Authors
  1. Robert C. Coffin
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  2. Jeff Peet
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  3. James Rogers
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  4. Guillermo C. Bazan
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Contributions

R.C.C. synthesized and characterized the polymers, J.P. fabricated and tested the solar cells, J.R. collected the SAED data, G.C.B. organized the project and directed data analysis.

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Correspondence to Guillermo C. Bazan.

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The authors declare no competing financial interests.

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Coffin, R., Peet, J., Rogers, J. et al. Streamlined microwave-assisted preparation of narrow-bandgap conjugated polymers for high-performance bulk heterojunction solar cells. Nature Chem 1, 657–661 (2009). https://doi.org/10.1038/nchem.403

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