Journal article
The role of charge recombination to triplet excitons in organic solar cells
- Abstract:
- The use of non-fullerene acceptors (NFAs) in organic solar cells has led to power conversion efficiencies as high as 18%<sup>1</sup>. However, organic solar cells are still less efficient than inorganic solar cells, which typically have power conversion efficiencies of more than 20%<sup>2</sup>. A key reason for this difference is that organic solar cells have low open-circuit voltages relative to their optical bandgaps<sup>3</sup>, owing to non-radiative recombination<sup>4</sup>. For organic solar cells to compete with inorganic solar cells in terms of efficiency, non-radiative loss pathways must be identified and suppressed. Here we show that in most organic solar cells that use NFAs, the majority of charge recombination under open-circuit conditions proceeds via the formation of non-emissive NFA triplet excitons; in the benchmark PM6:Y6 blend<sup>5</sup>, this fraction reaches 90%, reducing the open-circuit voltage by 60 mV. We prevent recombination via this non-radiative channel by engineering substantial hybridization between the NFA triplet excitons and the spin-triplet charge-transfer excitons. Modelling suggests that the rate of back charge transfer from spin-triplet charge-transfer excitons to molecular triplet excitons may be reduced by an order of magnitude, enabling re-dissociation of the spin-triplet charge-transfer exciton. We demonstrate NFA systems in which the formation of triplet excitons is suppressed. This work thus provides a design pathway for organic solar cells with power conversion efficiencies of 20% or more.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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- Files:
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(Preview, Accepted manuscript, 981.8KB, Terms of use)
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- Publisher copy:
- 10.1038/s41586-021-03840-5
Authors
- Publisher:
- Springer Nature
- Journal:
- Nature More from this journal
- Volume:
- 597
- Issue:
- 7878
- Pages:
- 666-671
- Place of publication:
- England
- Publication date:
- 2021-09-29
- Acceptance date:
- 2021-07-20
- DOI:
- EISSN:
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1476-4687
- ISSN:
-
0028-0836
- Pmid:
-
34588666
- Language:
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English
- Keywords:
- Pubs id:
-
1197695
- Local pid:
-
pubs:1197695
- Deposit date:
-
2021-11-05
Terms of use
- Copyright holder:
- Gillett et al.
- Copyright date:
- 2021
- Rights statement:
- © The Author(s), under exclusive licence to Springer Nature Limited 2021
- Notes:
- This is the accepted manuscript version of the article. The final version is available online from Springer Nature at: https://doi.org/10.1038/s41586-021-03840-5
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