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Harnessing singlet exciton fission to break the Shockley–Queisser limit


Singlet exciton fission is a carrier multiplication process in organic semiconductors that generates two electron–hole pairs for each photon absorbed. Singlet fission occurs on sub-100 fs timescales with yields of up to 200%, and photovoltaic devices based on singlet fission have achieved external quantum efficiencies above 100%. The major challenge for the field is to use singlet fission to improve the efficiency of conventional inorganic solar cells, such as silicon, and to break the Shockley–Queisser limit on the efficiency of single-junction photovoltaics. Achieving this goal requires a broader and more collaborative effort than the one used at present. Synthetic chemists, spectroscopists, theorists, materials scientists, device physicists and engineers will need to work together. In this Review, we critically assess the current status of the field, highlight the key results and identify the challenges ahead. In doing so, we seek to open the field to new expertise and ideas, which will in turn promote both fundamental science and device applications.

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Figure 1: The losses in an ideal silicon cell leading to the Shockley–Queisser limit.
Figure 2: The basic concept of singlet exciton fission.
Figure 3: Experimental detection of singlet exciton fission.
Figure 4: The mechanism of singlet exciton fission.
Figure 5: The concepts and schematics of devices enhanced by singlet exciton fission.
Figure 6: A schematic of the proposed singlet fission photon multiplier device.


  1. 1

    International Energy Agency Technology Roadmap Solar Photovoltaic Energy. IEA (2014).

  2. 2

    Lewis, N. S. Research opportunities to advance solar energy utilization. Science 351, aad1920 (2016).

    Article  CAS  Google Scholar 

  3. 3

    Shockley, W. & Queisser, H. J. Detailed balance limit of efficiency of p-n junction solar cells. J. Appl. Phys. 32, 510–519 (1961).

    CAS  Article  Google Scholar 

  4. 4

    Tanabe, K. A review of ultrahigh efficiency III-V semiconductor compound solar cells: multijunction tandem, lower dimensional, photonic up/down conversion and plasmonic nanometallic structures. Energies 2, 504–530 (2009).

    CAS  Article  Google Scholar 

  5. 5

    Polman, A. & Atwater, H. Photonic design principles for ultrahigh-efficiency photovoltaics. Nat. Mater. 11, 174–177 (2012).

    CAS  Article  Google Scholar 

  6. 6

    Pietryga, J. M. et al. Spectroscopic and device aspects of nanocrystal quantum dots. Chem. Rev. 116, 10513–10622 (2016).

    CAS  Article  Google Scholar 

  7. 7

    Semonin, O., Luther, J. & Beard, M. C. Multiple exciton generation in a quantum dot solar cell. SPIE Newsroom doi:10.1117/2.1201203.004146 (2012).

  8. 8

    Beard, M. C., Luther, J. M., Semonin, O. E. & Nozik, A. J. Third generation photovoltaics based on multiple exciton generation in quantum confined semiconductors. Acc. Chem. Res. 46, 1252–1260 (2013).

    CAS  Article  Google Scholar 

  9. 9

    Smith, M. & Michl, J. Singlet fission. Chem. Rev. 110, 6891–6936 (2010). A comprehensive review of the history of SF, molecules showing SF and possible design rules.

    CAS  Article  Google Scholar 

  10. 10

    Wilson, M. et al. Ultrafast dynamics of exciton fission in polycrystalline pentacene. J. Am. Chem. Soc. 133, 11830–11833 (2011). This study demonstrates that SF can occur on sub-100 fs timescales.

    CAS  Article  Google Scholar 

  11. 11

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

    CAS  Article  Google Scholar 

  12. 12

    Rao, A., Wilson, M. W. B., Albert-Seifried, S., Di Pietro, R. & Friend, R. H. Photophysics of pentacene thin films: the role of exciton fission and heating effects. Phys. Rev. B 84, 195411 (2011).

    Article  CAS  Google Scholar 

  13. 13

    Johnson, R. C. & Merrifield, R. E. Effects of magnetic fields on the mutual annihilation of triplet excitons in anthracene crystals. Phys. Rev. B 1, 896–902 (1970).

    Article  Google Scholar 

  14. 14

    Lee, J. et al. Singlet exciton fission photovoltaics. Acc. Chem. Res. 46, 1300–1311 (2013).

    CAS  Article  Google Scholar 

  15. 15

    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 

  16. 16

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

    Article  CAS  Google Scholar 

  17. 17

    Congreve, D. N. et al. External quantum efficiency above 100% in a singlet-exciton-fission–based organic photovoltaic cell. Science 340, 334–337 (2013). This study presents the first demonstration of an SF-enhanced PV device with an EQE above 100%.

    CAS  Article  Google Scholar 

  18. 18

    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 

  19. 19

    Sanders, S. N. et al. Exciton correlations in intramolecular singlet fission. J. Am. Chem. Soc. 138, 7289–7297 (2016).

    CAS  Article  Google Scholar 

  20. 20

    Sanders, S. N. et al. Intramolecular singlet fission in oligoacene heterodimers. Angew. Chem. Int. Ed. Engl. 55, 3373–3377 (2016).

    CAS  Article  Google Scholar 

  21. 21

    Köhler, A. & Bässler, H. Triplet states in organic semiconductors. Mater. Sci. Eng. R 66, 71–109 (2009).

    Article  CAS  Google Scholar 

  22. 22

    Tilley, A. J. et al. Ultrafast triplet formation in thionated perylene diimides. J. Phys. Chem. C 118, 9996–10004 (2014).

    CAS  Article  Google Scholar 

  23. 23

    Burdett, J. & Bardeen, C. 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). This study provides a demonstration of quantum beating in the photoluminescence of tetracene.

    CAS  Article  Google Scholar 

  24. 24

    Wang, R. et al. Magnetic dipolar interaction between correlated triplets created by singlet fission in tetracene crystals. Nat. Commun. 6, 8602 (2015).

    CAS  Article  Google Scholar 

  25. 25

    Weiss, L. R. et al. Strongly exchange-coupled triplet pairs in an organic semiconductor. Nat. Phys. 13, 176–181 (2016).

    Article  CAS  Google Scholar 

  26. 26

    Tayebjee, M. J. Y. et al. Quintet multiexciton dynamics in singlet fission. Nat. Phys. 13, 182–188 (2016).

    Article  CAS  Google Scholar 

  27. 27

    Burdett, J. J., Piland, G. & Bardeen, C. J. Magnetic field effects and the role of spin states in singlet fission. Chem. Phys. Lett. 585, 1–10 (2013). A review of magnetic field effects in SF.

    CAS  Article  Google Scholar 

  28. 28

    Bayliss, S. L. et al. Geminate and nongeminate recombination of triplet excitons formed by singlet fission. Phys. Rev. Lett. 112, 238701 (2014).

    Article  CAS  Google Scholar 

  29. 29

    Bayliss, S. L. et al. Spin signatures of exchange-coupled triplet pairs formed by singlet fission. Phys. Rev. B 94, 045204 (2016).

    Article  Google Scholar 

  30. 30

    Burdett, J. J. & Bardeen, C. J. The dynamics of singlet fission in crystalline tetracene and covalent analogs. Acc. Chem. Res. 46, 1312–1320 (2013).

    CAS  Article  Google Scholar 

  31. 31

    Tayebjee, M. J., Clady, R. G. & Schmidt, T. W. The exciton dynamics in tetracene thin films. Phys. Chem. Chem. Phys. 15, 14797–14805 (2013).

    CAS  Article  Google Scholar 

  32. 32

    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 

  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

    Lukman, S. et al. Tuning the role of charge-transfer states in intramolecular singlet exciton fission through side-group engineering. Nat. Commun. 7, 13622 (2016).

    CAS  Article  Google Scholar 

  35. 35

    Lukman, S. et al. Tuneable singlet exciton fission and triplet–triplet annihilation in an orthogonal pentacene dimer. Adv. Funct. Mater. 25, 5452–5461 (2015).

    CAS  Article  Google Scholar 

  36. 36

    Stern, H. L. et al. Vibronically coherent ultrafast triplet-pair formation and subsequent thermally activated dissociation control efficient endothermic singlet fission. Nat. Chem. (2017).

  37. 37

    Wang, C. & Tauber, M. J. High-yield singlet fission in a zeaxanthin aggregate observed by picosecond resonance Raman spectroscopy. J. Am. Chem. Soc. 132, 13988–13991 (2010).

    CAS  Article  Google Scholar 

  38. 38

    Musser, A. J. et al. Evidence for conical intersection dynamics mediating ultrafast singlet exciton fission. Nat. Phys. 13, 182–188 (2015). This study provides evidence for strong vibronic coupling dynamics mediating SF.

    Google Scholar 

  39. 39

    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 

  40. 40

    Chan, W. L. L. et al. Observing the multiexciton state in singlet fission and ensuing ultrafast multielectron transfer. Science 334, 1541–1545 (2011). This study presents the observation of ultrafast TT formation with time-resolved photoelectron spectroscopy.

    CAS  Article  Google Scholar 

  41. 41

    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 (2016).

    CAS  Article  Google Scholar 

  42. 42

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

    CAS  Article  Google Scholar 

  43. 43

    Chan, W. L. et al. The quantum coherent mechanism for singlet fission: experiment and theory. Acc. Chem. Res. 46, 1321–1329 (2013).

    CAS  Article  Google Scholar 

  44. 44

    Johnson, J. C., Nozik, A. J. & Michl, J. The role of chromophore coupling in singlet fission. Acc. Chem. Res. 46, 1290–1299 (2013).

    CAS  Article  Google Scholar 

  45. 45

    Wilson, M. W., Rao, A., Ehrler, B. & Friend, R. H. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices. Acc. Chem. Res. 46, 1330–1338 (2013).

    CAS  Article  Google Scholar 

  46. 46

    Zimmerman, P. M., Musgrave, C. B. & Head-Gordon, M. A correlated electron view of singlet fission. Acc. Chem. Res. 46, 1339–1347 (2013).

    CAS  Article  Google Scholar 

  47. 47

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

    CAS  Article  Google Scholar 

  48. 48

    Stern, H. L., Musser, A. J. & Friend, R. H. in Photochemistry 43, 270–285 (The Royal Society of Chemistry, 2016).

    Google Scholar 

  49. 49

    Beljonne, D., Yamagata, H., Brédas, J. L., Spano, F. C. & Olivier, Y. Charge-transfer excitations steer the Davydov splitting and mediate singlet exciton fission in pentacene. Phys. Rev. Lett. 110, 226402 (2013).

    CAS  Article  Google Scholar 

  50. 50

    Margulies, E. A. et al. Enabling singlet fission by controlling intramolecular charge transfer in π-stacked covalent terrylenediimide dimers. Nat. Chem. 8, 1120–1125 (2016).

    CAS  Article  Google Scholar 

  51. 51

    Scholes, G., Fleming, G., Olaya-Castro, A. & van Grondelle, R. Lessons from nature about solar light harvesting. Nat. Chem. 3, 763–774 (2011).

    CAS  Article  Google Scholar 

  52. 52

    Falke, S. et al. Coherent ultrafast charge transfer in an organic photovoltaic blend. Science 344, 1001–1005 (2014).

    CAS  Article  Google Scholar 

  53. 53

    Gélinas, S. et al. Ultrafast long-range charge separation in organic semiconductor photovoltaic diodes. Science 343, 512–516 (2014).

    Article  CAS  Google Scholar 

  54. 54

    Fuemmeler, E. G. et al. A direct mechanism of ultrafast intramolecular singlet fission in pentacene dimers. ACS Cent. Sci. 2, 316–324 (2016).

    CAS  Article  Google Scholar 

  55. 55

    Renaud, N. & Grozema, F. C. Intermolecular vibrational modes speed up singlet fission in perylenediimide crystals. J. Phys. Chem. Lett. 6, 360–365 (2015).

    CAS  Article  Google Scholar 

  56. 56

    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 

  57. 57

    Elenewski, J. E., Cubeta, U. S., Ko, E. & Chen, H. Functional mode singlet fission theory. J. Phys. Chem. C 121, 4130–4138 (2017).

    CAS  Article  Google Scholar 

  58. 58

    Tempelaar, R. & Reichman, D. R. Vibronic exciton theory of singlet fission. II. Two-dimensional spectroscopic detection of the correlated triplet pair state. J. Chem. Phys. 146, 174704 (2017).

    Article  CAS  Google Scholar 

  59. 59

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

    CAS  Article  Google Scholar 

  60. 60

    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 (2015).

    Article  CAS  Google Scholar 

  61. 61

    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 

  62. 62

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

    CAS  Article  Google Scholar 

  63. 63

    Le, A. K., Bender, J. A. & Roberts, S. T. Slow singlet fission observed in a polycrystalline perylenediimide thin film. J. Phys. Chem. Lett. 7, 4922–4928 (2016).

    CAS  Article  Google Scholar 

  64. 64

    Eaton, S. W. et al. Singlet exciton fission in polycrystalline thin films of a slip-stacked perylenediimide. J. Am. Chem. Soc. 135, 14701–14712 (2013).

    CAS  Article  Google Scholar 

  65. 65

    Eaton, S. W. et al. Singlet exciton fission in thin films of tert-butyl-substituted terrylenes. J. Phys. Chem. A 119, 4151–4161 (2015).

    CAS  Article  Google Scholar 

  66. 66

    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 

  67. 67

    Lu, L. et al. Recent advances in bulk heterojunction polymer solar cells. Chem. Rev. 115, 12666–12731 (2015).

    CAS  Article  Google Scholar 

  68. 68

    Li, X. & Tang, M. Triplet transport in thin films: fundamentals and applications. Chem. Commun. 53, 4429–4440 (2017).

    CAS  Article  Google Scholar 

  69. 69

    Reineke, S., Thomschke, M., Lüssem, B. & Leo, K. White organic light-emitting diodes: status and perspective. Rev. Mod. Phys. 85, 1245–1293 (2013).

    CAS  Article  Google Scholar 

  70. 70

    Kielar, M., Dhez, O., Pecastaings, G., Curutchet, A. & Hirsch, L. Long-term stable organic photodetectors with ultra low dark currents for high detectivity applications. Sci. Rep. 6, 39201 (2016).

    CAS  Article  Google Scholar 

  71. 71

    Dexter, D. L. Two ideas on energy transfer phenomena: ion-pair effects involving the OH stretching mode, and sensitization of photovoltaic cells. J. Lumin. 18, 779–784 (1979). This study presents seminal work showing how to use SF to enhance the efficiency of silicon solar cells.

    Article  Google Scholar 

  72. 72

    Nayak, P. K. & Cahen, D. Updated assessment of possibilities and limits for solar cells. Adv. Mater. 26, 1622–1628 (2014).

    CAS  Article  Google Scholar 

  73. 73

    Zhao, W. et al. Fullerene-free polymer solar cells with over 11% efficiency and excellent thermal stability. Adv. Mater. 28, 4734–4739 (2016).

    CAS  Article  Google Scholar 

  74. 74

    Liu, J. et al. Fast charge separation in a non-fullerene organic solar cell with a small driving force. Nat. Energy 1, 16089 (2016).

    CAS  Article  Google Scholar 

  75. 75

    Burke, T. M., Sweetnam, S., Vandewal, K. & McGehee, M. D. Beyond Langevin recombination: how equilibrium between free carriers and charge transfer states determines the open-circuit voltage of organic solar cells. Adv. Energy Mater. 5, 1500123 (2015).

    Article  CAS  Google Scholar 

  76. 76

    Lee, J., Jadhav, P. & Baldo, M. A. High efficiency organic multilayer photodetectors based on singlet exciton fission. Appl. Phys. Lett. 95, 033301 (2009).

    Article  CAS  Google Scholar 

  77. 77

    Jadhav, P. J. et al. Triplet exciton dissociation in singlet exciton fission photovoltaics. Adv. Mater. 24, 6169–6174 (2012).

    CAS  Article  Google Scholar 

  78. 78

    Thompson, N. J., Congreve, D. N., Goldberg, D., Menon, V. M. & Baldo, M. A. Slow light enhanced singlet exciton fission solar cells with a 126% yield of electrons per photon. Appl. Phys. Lett. 103, 263302 (2013).

    Article  CAS  Google Scholar 

  79. 79

    Ameri, T., Li, N. & Brabec, C. J. Highly efficient organic tandem solar cells: a follow up review. Energy Environ. Sci. 6, 2390–2413 (2013).

    CAS  Article  Google Scholar 

  80. 80

    O’Regan, B. & Gratzel, M. A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 353, 737–740 (1991).

    Article  Google Scholar 

  81. 81

    Shalini, S. et al. Status and outlook of sensitizers/dyes used in dye sensitized solar cells (DSSC): a review. Int. J. Energy Res. 40, 1303–1320 (2016).

    CAS  Article  Google Scholar 

  82. 82

    Ehrler, B., Musselman, K. P., Böhm, M. L., Friend, R. H. & Greenham, N. C. Hybrid pentacene/a-silicon solar cells utilizing multiple carrier generation via singlet exciton fission. Appl. Phys. Lett. 101, 153507 (2012).

    Article  CAS  Google Scholar 

  83. 83

    Yang, L. et al. Solution-processable singlet fission photovoltaic devices. Nano Lett. 15, 354–358 (2015).

    CAS  Article  Google Scholar 

  84. 84

    National Renewable Energy Laboratory. PV efficiency chart. NREL (2017).

  85. 85

    Tabachnyk, M. et al. Resonant energy transfer of triplet excitons from pentacene to PbSe nanocrystals. Nat. Mater. 13, 1033–1038 (2014). This study demonstrates efficient triplet transfer from pentacene to PbSe nanoparticles.

    CAS  Article  Google Scholar 

  86. 86

    Thompson, N. J. et al. Energy harvesting of non-emissive triplet excitons in tetracene by emissive PbS nanocrystals. Nat. Mater. 13, 1039–1043 (2014). This study demonstrates efficient triplet transfer from tetracene to PbS nanoparticles.

    CAS  Article  Google Scholar 

  87. 87

    Huang, Z. et al. Hybrid molecule–nanocrystal photon upconversion across the visible and near-infrared. Nano Lett. 15, 5552–5557 (2015).

    CAS  Article  Google Scholar 

  88. 88

    Mahboub, M., Maghsoudiganjeh, H., Pham, A., Huang, Z. & Tang, M. Triplet energy transfer from PbS(Se) nanocrystals to rubrene: the relationship between the upconversion quantum yield and size. Adv. Func. Mater. 26, 6091–6097 (2016).

    CAS  Article  Google Scholar 

  89. 89

    Mongin, C., Garakyaraghi, S., Razgoniaeva, N., Zamkov, M. & Castellano, F. N. Direct observation of triplet energy transfer from semiconductor nanocrystals. Science 351, 369–372 (2016).

    CAS  Article  Google Scholar 

  90. 90

    Wu, M. et al. Solid-state infrared-to-visible upconversion sensitized by colloidal nanocrystals. Nat. Photon. 10, 31–34 (2015).

    Article  CAS  Google Scholar 

  91. 91

    Piland, G. B. et al. Dynamics of molecular excitons near a semiconductor surface studied by fluorescence quenching of polycrystalline tetracene on silicon. Chem. Phys. Lett. 601, 33–38 (2014).

    CAS  Article  Google Scholar 

  92. 92

    Scholes, G. D. et al. Nanocrystal shape and the mechanism of exciton spin relaxation. Nano Lett. 6, 1765–1771 (2006).

    CAS  Article  Google Scholar 

  93. 93

    Liu, H. et al. Predicting the outdoor performance of flat-plate III–V/Si tandem solar cells. Solar Energy 149, 77–84 (2017).

    CAS  Article  Google Scholar 

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A.R. and R.H.F. thank M. Taybjee and J. Allardice for help with preparing Fig. 3b,c. A.R. and R.H.F. thank the Engineering and Physical Sciences Research Council (EPSRC) and the Winton Programme for the Physics of Sustainability for funding.

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A.R. obtained the data for the article. Both authors made substantial contributions to the content, wrote the manuscript and reviewed and/or edited the manuscript before submission.

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Correspondence to Akshay Rao.

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Rao, A., Friend, R. Harnessing singlet exciton fission to break the Shockley–Queisser limit. Nat Rev Mater 2, 17063 (2017).

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