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Delocalization boosts charge separation in organic solar cells

Polymer Journal volume 52, pages 691–700 (2020)Cite this article

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Abstract

Organic solar cells (OSCs) utilizing π-conjugated polymers have attracted widespread interest over the past three decades because of their potential advantages, including low weight, thin film flexibility, and low-cost manufacturing. However, their power conversion efficiency (PCE) has been far below that of inorganic analogs. Geminate recombination of charge transfer excitons is a major loss process in OSCs. This paper reviews our recent progress in using transient absorption spectroscopy to understand geminate recombination in bulk heterojunction OSCs, including the impact of polymer crystallinity on charge generation and dissociation mechanisms in nonfullerene acceptor-based OSCs. The first example of a high PCE with a small photon energy loss is also presented. The importance of delocalization of the charge wave function to suppress geminate recombination is highlighted by this focus review.

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Acknowledgements

The author thanks Prof Sir Richard Friend, Dr S. Matthew Menke, Prof Itaru Osaka, Prof Shinzaburo Ito, and Prof Hideo Ohkita for fruitful discussions. The author also thanks all other collaborators. This work was partly supported by JSPS Postdoctoral Fellowships for Research Abroad, JSPS KAKENHI Grant-in-Aid for Young Scientists (B) No. 17K14527, and JST PRESTO program Grant Number JPMJPR1874. The author also acknowledges financial support from Trycom Advance Co., Ltd.

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

    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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Tamai, Y. Delocalization boosts charge separation in organic solar cells. Polym J 52, 691–700 (2020). https://doi.org/10.1038/s41428-020-0339-4

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