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Endothermic singlet fission is hindered by excimer formation


Singlet fission is a process whereby two triplet excitons can be produced from one photon, potentially increasing the efficiency of photovoltaic devices. Endothermic singlet fission is desired for a maximum energy-conversion efficiency, and such systems have been considered to form an excimer-like state with multiexcitonic character prior to the appearance of triplets. However, the role of the excimer as an intermediate has, until now, been unclear. Here we show, using 5,12-bis((triisopropylsilyl)ethynyl)tetracene in solution as a prototypical example, that, rather than acting as an intermediate, the excimer serves to trap excited states to the detriment of singlet-fission yield. We clearly demonstrate that singlet fission and its conjugate process, triplet–triplet annihilation, occur at a longer intermolecular distance than an excimer intermediate would impute. These results establish that an endothermic singlet-fission material must be designed to avoid excimer formation, thus allowing singlet fission to reach its full potential in enhancing photovoltaic energy conversion.

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Figure 1: Schematic Marcus–Hush–Morse free-energy surface of the SF–TTA process.
Figure 2: Emission spectra of concentrated TIPS-Tc solutions.
Figure 3: TRPL of concentrated TIPS-Tc in toluene. The emission spectrum reverts to being dominated by the S1 state after excimer decay.
Figure 4: Extracted spectra and their time-dependent weightings.
Figure 5: Experimental and simulated TA heat maps with extracted spectra and time dependences.


  1. 1

    Smith, M. B. & Michl, J. Recent advances in singlet fission. Annu. Rev. Phys. Chem. 64, 361–386 (2013).

    CAS  Article  Google Scholar 

  2. 2

    Smith, M. B. & Michl, J. Singlet fission. Chem. Rev. 110, 6891–6936 (2010).

    CAS  Article  Google Scholar 

  3. 3

    Chan, W.-L. et al. Observing the multiexciton state in singlet fission and ensuing ultrafast multielectron transfer. Science 334, 1541–1545 (2011).

    CAS  Article  Google Scholar 

  4. 4

    Walker, B. J., Musser, A. J., Beljonne, D. & Friend, R. H. Singlet exciton fission in solution. Nat. Chem. 5, 1019–1024 (2013).

    CAS  Article  Google Scholar 

  5. 5

    Yost, S. R. et al. A transferable model for singlet-fission kinetics. Nat. Chem. 6, 492–497 (2014).

    CAS  Article  Google Scholar 

  6. 6

    Zimmerman, P. M., Zhang, Z. & Musgrave, C. B. Singlet fission in pentacene through multi-exciton quantum states. Nat. Chem. 2, 648–652 (2010).

    CAS  Article  Google Scholar 

  7. 7

    Zirzlmeier, J. et al. Singlet fission in pentacene dimers. Proc. Natl Acad. Sci. USA 112, 5325–5330 (2015).

    CAS  Article  Google Scholar 

  8. 8

    Pensack, R. D. et al. Observation of two triplet-pair intermediates in singlet exciton fission. J. Phys. Chem. Lett. 7, 2370–2375 (2016).

    CAS  Article  Google Scholar 

  9. 9

    Morrison, A. F. & Herbert, J. M. Evidence for singlet fission driven by vibronic coherence in crystalline tetracene. J. Phys. Chem. Lett. 8, 1442–1448 (2017).

    CAS  Article  Google Scholar 

  10. 10

    Zimmerman, P. M., Bell, F., Casanova, D. & Head-Gordon, M. Mechanism for singlet fission in pentacene and tetracene: from single exciton to two triplets. J. Am. Chem. Soc. 133, 19944–19952 (2011).

    CAS  Article  Google Scholar 

  11. 11

    Chan, W.-L., Ligges, M. & Zhu, X.-Y. The energy barrier in singlet fission can be overcome through coherent coupling and entropic gain. Nat. Chem. 4, 840–845 (2012).

    CAS  Article  Google Scholar 

  12. 12

    Feng, X. & Krylov, A. I. On couplings and excimers: lessons from studies of singlet fission in covalently linked tetracene dimers. Phys. Chem. Chem. Phys. 18, 7751–7761 (2016).

    CAS  Article  Google Scholar 

  13. 13

    Burdett, J. J. & Bardeen, C. J. Quantum beats in crystalline tetracene delayed fluorescence due to triplet pair coherences produced by direct singlet fission. J. Am. Chem. Soc. 134, 8597–8607 (2012).

    CAS  Article  Google Scholar 

  14. 14

    Monahan, N. & Zhu, X.-Y. Charge transfer-mediated singlet fission. Annu. Rev. Phys. Chem. 66, 601–618 (2015).

    CAS  Article  Google Scholar 

  15. 15

    Bakulin, A. A. et al. Real-time observation of multiexcitonic states in ultrafast singlet fission using coherent 2D electronic spectroscopy. Nat. Chem. 8, 16–23 (2015).

    Article  Google Scholar 

  16. 16

    Musser, A. J. et al. Evidence for conical intersection dynamics mediating ultrafast singlet exciton fission. Nat. Phys. 11, 352–357 (2015).

    CAS  Article  Google Scholar 

  17. 17

    Busby, E. et al. A design strategy for intramolecular singlet fission mediated by charge-transfer states in donor–acceptor organic materials. Nat. Mater. 14, 426–433 (2015).

    CAS  Article  Google Scholar 

  18. 18

    Monahan, N. R. et al. Dynamics of the triplet-pair state reveals the likely coexistence of coherent and incoherent singlet fission in crystalline hexacene. Nat. Chem. 9, 341–346 (2016).

    Article  Google Scholar 

  19. 19

    Ehrler, B. et al. In situ measurement of exciton energy in hybrid singlet-fission solar cells. Nat. Commun. 3, 1019 (2012).

    Article  Google Scholar 

  20. 20

    Ehrler, B., Wilson, M. W. B., Rao, A., Friend, R. H. & Greenham, N. C. Singlet exciton fission-sensitized infrared quantum dot solar cells. Nano Lett. 12, 1053–1057 (2012).

    CAS  Article  Google Scholar 

  21. 21

    Congreve, D. N. et al. External quantum efficiency above 100% in a singlet-exciton-fission-based organic photovoltaic cell. Science 340, 334–337 (2013).

    CAS  Article  Google Scholar 

  22. 22

    Tritsch, J. R., Chan, W.-L., Wu, X., Monahan, N. R. & Zhu, X.-Y. Harvesting singlet fission for solar energy conversion via triplet energy transfer. Nat. Commun. 4, 2679 (2013).

    Article  Google Scholar 

  23. 23

    Tayebjee, M. J. Y., McCamey, D. R. & Schmidt, T. W. Beyond Shockley–Queisser: molecular approaches to high-efficiency photovoltaics. J. Phys. Chem. Lett. 6, 2367–2378 (2015).

    CAS  Article  Google Scholar 

  24. 24

    Tayebjee, M. J. Y., Gray-Weale, A. A. & Schmidt, T. W. Thermodynamic limit of exciton fission solar cell efficiency. J. Phys. Chem. Lett. 3, 2749–2754 (2012).

    CAS  Article  Google Scholar 

  25. 25

    Tayebjee, M. J. Y., Clady, R. G. C. R. & Schmidt, T. W. The exciton dynamics in tetracene thin films. Phys. Chem. Chem. Phys. 15, 14797 (2013).

    CAS  Article  Google Scholar 

  26. 26

    Wilson, M. W. B. et al. Temperature-independent singlet exciton fission in tetracene. J. Am. Chem. Soc. 135, 16680–16688 (2013).

    CAS  Article  Google Scholar 

  27. 27

    Arias, D. H., Ryerson, J. L., Cook, J. D., Damrauer, N. H. & Johnson, J. C. Polymorphism influences singlet fission rates in tetracene thin films. Chem. Sci. 7, 1185–1191 (2016).

    CAS  Article  Google Scholar 

  28. 28

    Piland, G. B. & Bardeen, C. J. How morphology affects singlet fission in crystalline tetracene. J. Phys. Chem. Lett. 6, 1841–1846 (2015).

    CAS  Article  Google Scholar 

  29. 29

    Lim, S.-H., Bjorklund, T. G., Spano, F. C. & Bardeen, C. J. Exciton delocalization and superradiance in tetracene thin films and nanoaggregates. Phys. Rev. Lett. 92, 107402 (2004).

    Article  Google Scholar 

  30. 30

    Burdett, J. J., Gosztola, D. & Bardeen, C. J. The dependence of singlet exciton relaxation on excitation density and temperature in polycrystalline tetracene thin films: kinetic evidence for a dark intermediate state and implications for singlet fission. J. Chem. Phys. 135, 214508 (2011).

    Article  Google Scholar 

  31. 31

    Stern, H. L. et al. Identification of a triplet pair intermediate in singlet exciton fission in solution. Proc. Natl Acad. Sci. USA 112, 7656–7661 (2015).

    CAS  Article  Google Scholar 

  32. 32

    Mauck, C. M. et al. Singlet fission via an excimer-like intermediate in 3,6-bis(thiophen-2-yl)diketopyrrolopyrrole derivatives. J. Am. Chem. Soc. 138, 11749–11761 (2016).

    CAS  Article  Google Scholar 

  33. 33

    Korovina, N. V. et al. Singlet fission in a covalently linked cofacial alkynyltetracene dimer. J. Am. Chem. Soc. 138, 617–627 (2016).

    CAS  Article  Google Scholar 

  34. 34

    Schrauben, J. N., Ryerson, J. L., Michl, J. & Johnson, J. C. Mechanism of singlet fission in thin films of 1,3-diphenylisobenzofuran. J. Am. Chem. Soc. 136, 7363–7373 (2014).

    CAS  Article  Google Scholar 

  35. 35

    Ryerson, J. L. et al. Two thin film polymorphs of the singlet fission compound 1,3-diphenylisobenzofuran. J. Phys. Chem. C 118, 12121–12132 (2014).

    CAS  Article  Google Scholar 

  36. 36

    Parker, C. A. & Hatchard, C. G. Delayed fluorescence from solutions of anthracene and phenanthrene. Proc. R. Soc. A 269, 574–584 (1962).

    Article  Google Scholar 

  37. 37

    Odom, S. A., Parkin, S. R. & Anthony, J. E. Tetracene derivatives as potential red emitters for organic LEDs. Org. Lett. 5, 4245–4248 (2003).

    CAS  Article  Google Scholar 

  38. 38

    Khoury, T. & Crossley, M. J. A strategy for the stepwise ring annulation of all four pyrrolic rings of a porphyrin. Chem. Commun. 4851–4853 ( 2007).

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T.W.S. acknowledges the Australian Research Council for a Future Fellowship (FT130100177). This work was supported by the Australian Research Council (Centre of Excellence in Exciton Science CE170100026, DP160103797, LE0989747).

Author information




C.B.D. and L.F. performed the measurements. C.B.D., J.K.G. and L.F. analysed the data. A.J.P. synthesized the TIPS-Tc material. J.E.A. designed and provided the TIPS-Tc material. M.J.C. designed and provided the PdPQ4 material. T.W.S., J.K.G. and L.F. wrote the manuscript. J.K.G. and C.B.D. designed the figures with input from T.W.S. C.B.D. and P.C.T. performed the TA experiments. T.W.K. provided access to and advice on the TA experiments, and critically read the manuscript. T.W.S. conceived the experiments and performed the modelling.

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Correspondence to Timothy W. Schmidt.

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The authors declare no competing financial interests.

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Dover, C., Gallaher, J., Frazer, L. et al. Endothermic singlet fission is hindered by excimer formation. Nature Chem 10, 305–310 (2018).

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