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Delocalization suppresses nonradiative charge recombination in polymer solar cells

Polymer Journal volume 54, pages 1345–1353 (2022)Cite this article

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Abstract

Suppressing nonradiative deactivation of charge transfer (CT) states is pivotal to realizing further improvements in the power conversion efficiencies of polymer solar cells (PSCs). According to the energy gap law, the nonradiative decay rate constant knr scales exponentially with decreasing CT state energy ECT; thereby, as long as knr is governed by the energy gap law, a decrease in ECT will inevitably increase nonradiative deactivation of CT states and hence decrease the power conversion efficiency. Here, we report the nonradiative decay dynamics of CT states generated in various nonfullerene-acceptor-based PSCs by using transient absorption spectroscopy. The absence of a strong correlation between knr and ECT indicates that the energy gap law is not valid for these PSCs and that parameters other than ECT contribute significantly to knr. We found that knr decreased with an increase in materials’ crystallinities, indicating that increasing crystallinity leads to CT state delocalization, which in turn mitigates the nonradiative deactivation of CT states.

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The data supporting the results of this work are available from the corresponding author upon reasonable request.

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Acknowledgements

This study was partly supported by JST PRESTO program Grant Number JPMJPR1874, JSPS KAKENHI Grant Numbers 17K14527, 21H02012, and 21H05394, The Murata Science Foundation, The Sumitomo Foundation, and Ogasawara Toshiaki Memorial Foundation.

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Authors and Affiliations

  1. Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo, Kyoto, 615-8510, Japan

    Shin-ichiro Natsuda, Toshiharu Saito, Rei Shirouchi, Kenta Imakita & Yasunari Tamai

  2. Japan Science and Technology Agency (JST), PRESTO, 4-1-8 Honcho Kawaguchi, Saitama, 332-0012, Japan

    Yasunari Tamai

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  1. Shin-ichiro Natsuda
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Natsuda, Si., Saito, T., Shirouchi, R. et al. Delocalization suppresses nonradiative charge recombination in polymer solar cells. Polym J 54, 1345–1353 (2022). https://doi.org/10.1038/s41428-022-00685-1

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