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A bending test protocol for characterizing the mechanical performance of flexible photovoltaics

Nature Energy volume 9, pages 1335–1343 (2024)Cite this article

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Abstract

Flexible photovoltaic (PV) devices are a promising research field with potential for wearable, portable, indoor and internet-of-things applications. Substantial progress has been made in recent years, with flexible emerging PVs reporting power conversion efficiencies (PCEs) of over 24%. Yet, there is a need for a unifying protocol to assess PV performance, compare research results, and evaluate state-of-the-art achievements in flexible PVs. Here we present a protocol for measuring PCE over 1,000 bending cycles under 1% strain. Moreover, several good practice guidelines are proposed, including those related to bending procedures, flexibility testing with and without encapsulation, and ambient conditions during testing (for example, temperature, humidity and illumination). Notably, the importance of the uniform application of the bending radius and the testing of parallel and perpendicular orientations of the bending axis with respect to the direction of the electric current are emphasized. These recommendations aim to promote consistency in device comparison and allow for better reproducibility.

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Fig. 1: Bending set-ups.
Fig. 2: Sample bending.
Fig. 3: Encapsulation and bending.

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Acknowledgements

This study was supported by the Japan Society for the Promotion of Science under Grants-in-Aid for Scientific Research (S) (no. JP22H04949). K. Fukuda acknowledges support from JST ASPIRE for Rising Scientists (JPMJAP2336). O.A. acknowledges the Juan de la Cierva Fellowship grant FJC2021-046887-I funded by MICIU/AEI/10.13039/501100011033 and by the European Union Next Generation EU/PRTR. K. Forberich acknowledges support by the Helmholtz Association in the framework of the innovation platform ‘Solar TAP’. A.W.Y.H.-B is supported by the Australian Research Council (ARC) via Future Fellowship FT210100210. N.P.P. acknowledges support from US DOE EERE SETO (DE-EE0009511). We thank S. Xiong of RIKEN (Japan) for his support with the photography of the bending set-ups.

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Authors and Affiliations

  1. Thin-Film Device Laboratory, RIKEN, Wako, Saitama, Japan

    Kenjiro Fukuda, Lulu Sun & Takao Someya

  2. RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, Japan

    Kenjiro Fukuda, Baocai Du & Takao Someya

  3. Department of Electrical Engineering and Information Systems, The University of Tokyo, Tokyo, Japan

    Baocai Du, Masahito Takakuwa & Takao Someya

  4. Institute of Engineering Innovation, Graduate School of Engineering, The University of Tokyo, Tokyo, Japan

    Masahito Takakuwa

  5. Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zürich, Zürich, Switzerland

    Jiachen Wang

  6. Department of Electronic, Electrical and Automatic Engineering, Universitat Rovira i Virgili, Tarragona, Spain

    Lluis F. Marsal & Osbel Almora

  7. Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China

    Yinhua Zhou

  8. College of Chemistry and Chemical Engineering/Institute of Polymers and Energy Chemistry (IPEC), Nanchang University, Nanchang, China

    Yiwang Chen

  9. State Key Laboratory of Silicon and Advanced Semiconductor Materials, International Research Center for X Polymers, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, P. R. China

    Hongzheng Chen

  10. University of Surrey, Guildford, Surrey, UK

    S. Ravi P. Silva

  11. Material Science and Engineering Program (MSE), Physical Sciences and Engineering Division (PSE), King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia

    Derya Baran

  12. Centre for Hybrid and Organic Solar Energy, Electronic Engineering Department, University of Rome Tor Vergata, Rome, Italy

    Luigi A. Castriotta & Thomas M. Brown

  13. School of Energy and Chemical Engineering, Perovtronics Research Center, and Graduate School of Carbon Neutrality, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea

    Changduk Yang

  14. State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing, China

    Weiwei Li

  15. School of Physics and Sydney Nano Institute, The University of Sydney, Sydney, New South Wales, Australia

    Anita W. Y. Ho-Baillie

  16. Epishine AB, Linköping, Sweden

    Thomas Österberg

  17. School of Engineering, Brown University, Providence, RI, USA

    Nitin P. Padture

  18. Forschungszentrum Jülich GmbH, Department of High Throughput Methods in Photovoltaics, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (HI ERN), Erlangen, Germany

    Karen Forberich & Christoph J. Brabec

  19. Institute of Materials for Electronics and Energy Technology (i-MEET), Department of Materials Science and Engineering, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

    Christoph J. Brabec

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  1. Kenjiro Fukuda
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Correspondence to Kenjiro Fukuda or Osbel Almora.

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Supplementary Data 1

Bending test checklist for characterization of mechanical performance of flexible solar cells

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Fukuda, K., Sun, L., Du, B. et al. A bending test protocol for characterizing the mechanical performance of flexible photovoltaics. Nat Energy 9, 1335–1343 (2024). https://doi.org/10.1038/s41560-024-01651-2

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