Singlet fission (SF) can potentially boost the efficiency of solar energy conversion by converting a singlet exciton (S1) into two free triplets (T1 + T1) through an intermediate state of a correlated triplet pair (TT). Although efficient TT generation has been recently realized in many intramolecular SF materials, their potential applications have been hindered by the poor efficiency of TT dissociation. Here we demonstrate that this can be overcome by employing a spatially separated 1(T…T) state with weak intertriplet coupling in tetracene oligomers with three or more chromophores. By using transient magneto-optical spectroscopic methods, we show that free-triplet generation can be markedly enhanced through the SF pathway that involves the spatially separated 1(T…T) state rather than the pathway mediated by the spatially adjacent TT state, leading to a marked improvement in free-triplet generation with an efficiency increase from 21% for the dimer to 85% (124%) for the trimer (tetramer).
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The data shown in the paper are available from the figshare repository at https://doi.org/10.6084/m9.figshare.13669820.
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This work was supported by the National Key R&D Program of China (2017YFA0303703 and 2018YFA0209100), the National Natural Science Foundation of China (21922302, 21873047, 91850105, 91833305, 21722302 and 21673109), Jiangsu Provincial Funds for Distinguished Young Scientists (BK20160019), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and the Fundamental Research Funds for the Central Universities (0204-14380126). C.Z. acknowledges financial support from the Tang Scholar programme. We thank X. Wu for technical assistance. We are grateful to the High-Performance Computing Center of Nanjing University for performing the numerical calculations in this paper on its blade cluster system.
The authors declare no competing interests.
Peer review information Nature Chemistry thanks T. Schmidt and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Wang, Z., Liu, H., Xie, X. et al. Free-triplet generation with improved efficiency in tetracene oligomers through spatially separated triplet pair states. Nat. Chem. (2021). https://doi.org/10.1038/s41557-021-00665-7