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Nano Research Energy 2024, 3: e9120099 https://doi.org/10.26599/NRE.2023.9120099
Research Article | Open Access | Issue | Published: 22 September 2023

Dissociation of singlet excitons dominates photocurrent improvement in high-efficiency non-fullerene organic solar cells

Show Author's Information Qicong Li1,2,§,  Shizhong Yue1,§,  Zhitao Huang1,  Chao Li1,  Jiaqian Sun1,  Keqian Dong1,  Zhijie Wang1( ),  Kong Liu1( ),  Shengchun Qu1( ),  Yong Lei3( )
Key Laboratory of Semiconductor Materials Science, Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
China Electronics Standardization Institution, Beijing 100007, China
Fachgebiet Angewandte Nanophysik, Institut für Physik & IMN MacroNano, Technische Universität Ilmenau, Ilmenau 98693, Germany

§ Qicong Li and Shizhong Yue contributed equally to this work.

Keywords:
organic solar cell, high efficiency, polarized light, singlet/triplet exciton
Cite this article:
Li Q, Yue S, Huang Z, et al. Dissociation of singlet excitons dominates photocurrent improvement in high-efficiency non-fullerene organic solar cells. Nano Research Energy, 2024, 3: e9120099. https://doi.org/10.26599/NRE.2023.9120099
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Abstract Full text Electronic supplementary material About this article

In organic solar cells, the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state. Therefore, the ratio of the singlet and triplet excitons directly affects the photocurrent. Many methods were used to optimize the performance of the low-efficiency solar cell by improving the ratio of triplet excitons, which shows a long diffusion length. Here we observed that in high-efficiency systems, the proportion of singlet excitons under linearly polarized light excitation is higher than that of circularly polarized light. Since the singlet charge transfer state has lower binding energy than the triplet state, it makes a significant contribution to the charge carrier generation and enhancement of the photocurrent. Further, the positive magnetic field effect reflects that singlet excitons dissociation plays a major role in the photocurrent, which is opposite to the case of low-efficiency devices where triplet excitons dominate the photocurrent.


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About this article

Dissociation of singlet excitons dominates photocurrent improvement in high-efficiency non-fullerene organic solar cells

Show Author's information Qicong Li1,2,§, Shizhong Yue1,§, Zhitao Huang1, Chao Li1, Jiaqian Sun1, Keqian Dong1, Zhijie Wang1( ), Kong Liu1( ), Shengchun Qu1( ), Yong Lei3( )
Key Laboratory of Semiconductor Materials Science, Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
China Electronics Standardization Institution, Beijing 100007, China
Fachgebiet Angewandte Nanophysik, Institut für Physik & IMN MacroNano, Technische Universität Ilmenau, Ilmenau 98693, Germany

§ Qicong Li and Shizhong Yue contributed equally to this work.

Abstract

In organic solar cells, the singlet and triplet excitons dissociate into free charge carriers with different mechanisms due to their opposite spin state. Therefore, the ratio of the singlet and triplet excitons directly affects the photocurrent. Many methods were used to optimize the performance of the low-efficiency solar cell by improving the ratio of triplet excitons, which shows a long diffusion length. Here we observed that in high-efficiency systems, the proportion of singlet excitons under linearly polarized light excitation is higher than that of circularly polarized light. Since the singlet charge transfer state has lower binding energy than the triplet state, it makes a significant contribution to the charge carrier generation and enhancement of the photocurrent. Further, the positive magnetic field effect reflects that singlet excitons dissociation plays a major role in the photocurrent, which is opposite to the case of low-efficiency devices where triplet excitons dominate the photocurrent.

Keywords: organic solar cell, high efficiency, polarized light, singlet/triplet exciton

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Publication history

Received: 09 July 2023
Revised: 23 August 2023
Accepted: 31 August 2023
Published: 22 September 2023
Issue date: March 2024

Copyright

© The Author(s) 2023. Published by Tsinghua University Press.

Acknowledgements

Acknowledgements

This study was financially supported by the National Key Research and Development Program of China (No. 2018YFE0204000), the National Natural Science Foundation of China (Nos. U20A20206, 51972300, 62274155, and 21975245), the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB43000000), and the Key Research Program of Frontier Science, Chinese Academy of Sciences (No. QYZDBSSW-SLH006). K. L. appreciates the support from the Youth Innovation Promotion Association, the Chinese Academy of Sciences (No. 2020114), and the Beijing Nova Program (No. 2020117).

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