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Reducing the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells

Nature Materials volume 16, pages 363–369 (2017)Cite this article

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Abstract

Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V.

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Figure 1: Chemical structures, energy levels and optical properties of materials used in this study.
Figure 2: Microstructural analysis of P3HT:IDTBR:IDFBR ternary blend.
Figure 3: Photovoltaic performances and EQE profiles of binary and ternary devices.
Figure 4: Charge carrier dynamics of inverted P3HT:IDTBR and P3HT:IDTBR:IDFBR devices.
Figure 5: Storage lifetime and photo-stability of P3HT:IDTBR:IDFBR and high-efficiency, low-bandgap polymer:fullerene devices.

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Acknowledgements

D.B. thanks Helmholtz Association for a Helmholtz Postdoc Fellowship. S.H. thanks BASF for financial support. The authors acknowledge EC FP7 Project SC2 (610115), EC FP7 Project ArtESun (604397), and EPSRC Project EP/G037515/1 and EP/K030671/1, EC FP7 Project POLYMED (612538) and Project Synthetic carbon allotropes project SFB 953.

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Author notes

  1. Derya Baran and Raja Shahid Ashraf: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, UK

    Derya Baran, Raja Shahid Ashraf, Sarah Holliday, Andrew Wadsworth, Sarah Lockett, James R. Durrant & Iain McCulloch

  2. King Abdullah University of Science and Technology (KAUST), KSC, Thuwal 23955-6900, Saudi Arabia

    Derya Baran, Raja Shahid Ashraf, Maged Abdelsamie, Marios Neophytou, Aram Amassian & Iain McCulloch

  3. IEK5-Photovoltaics, Forschungszentrum Jülich, 52425 Jülich, Germany

    Derya Baran & Thomas Kirchartz

  4. Department of Materials Science and Engineering, Stanford University, 476 Lomita Mall, Stanford, California 94305, USA

    David A. Hanifi & Alberto Salleo

  5. Institute of Materials for Electronics and Energy Technology (I-MEET), Friedrich-Alexander-University Erlangen-Nuremberg, 91058 Erlangen, Germany

    Nicola Gasparini & Christoph J. Brabec

  6. Department of Physics and Center of Plastic Electronics, Imperial College London, London SW7 2AZ, UK

    Jason A. Röhr, Christopher J. M. Emmott & Jenny Nelson

  7. Grantham Institute for Climate Change and the Environment, Imperial College London, London SW7 2AZ, UK

    Christopher J. M. Emmott & Jenny Nelson

  8. Faculty of Engineering and CENIDE, University of Duisburg-Essen, Carl-Benz-Straße 199, 47057 Duisburg, Germany

    Thomas Kirchartz

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Contributions

D.B. and R.S.A. prepared the manuscript. S.H. and A.W. synthesized the non-fullerene acceptors. R.S.A. fabricated and characterized solar cell devices. D.B. and N.G. carried out CE and TPV measurements. M.A. performed the in situ GIWAXS and UV–Vis absorption measurements during spin coating. D.A.H. performed static GIWAXS measurements. J.A.R. did the SCLC measurements. S.L. performed the DSC measurements. R.S.A. and M.N. performed stability measurements. C.J.M.E. helped J.N. with EROI modelling. All authors discussed the results and commented on the manuscript. C.J.B. supervised charge extraction measurements. J.R.D. supervised TPV measurements, A.A. supervised in situ GIWAXS and UV–Vis measurements, A.S. supervised static GIWAXS measurements, T.K. and J.N. supervised SCLC, electroluminescence and EQE measurements. I.M. revised the manuscript and supervised and directed the project.

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Correspondence to Derya Baran, Raja Shahid Ashraf or Iain McCulloch.

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Baran, D., Ashraf, R., Hanifi, D. et al. Reducing the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells. Nature Mater 16, 363–369 (2017). https://doi.org/10.1038/nmat4797

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