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A unified description of non-radiative voltage losses in organic solar cells


Recent advances in organic solar cells based on non-fullerene acceptors (NFAs) come with reduced non-radiative voltage losses (ΔVnr). Here we show that, in contrast to the energy-gap-law dependence observed in conventional donor:fullerene blends, the ΔVnr values in state-of-the-art donor:NFA organic solar cells show no correlation with the energies of charge-transfer electronic states at donor:acceptor interfaces. By combining temperature-dependent electroluminescence experiments and dynamic vibronic simulations, we provide a unified description of ΔVnr for both fullerene- and NFA-based devices. We highlight the critical role that the thermal population of local exciton states plays in low-ΔVnr systems. An important finding is that the photoluminescence yield of the pristine materials defines the lower limit of ΔVnr. We also demonstrate that the reduction in ΔVnr (for example, <0.2 V) can be obtained without sacrificing charge generation efficiency. Our work suggests designing donor and acceptor materials with high luminescence efficiency and complementary optical absorption bands extending into the near-infrared region.

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Fig. 1: Emission spectral lineshapes of D:A blends as a function of tLE−CT and ΔELECT.
Fig. 2: Non-radiative voltage losses as a function of ΔELE−CT and tLE−CT.
Fig. 3: ΔVnr versus interfacial ECT.
Fig. 4: Charge generation efficiencies versus device ΔVnr.

Data availability

The authors declare that all relevant data are included in the paper and its Supplementary Information.

Code availability

The codes used in this paper are deposited on GitHub (


  1. 1.

    Best Research-Cell Efficiencies (National Renewable Energy Laboratory, 2020);

  2. 2.

    Liu, Q. et al. 18% Efficiency organic solar cells. Sci. Bull. 65, 272–275 (2020).

    Google Scholar 

  3. 3.

    Zhang, M. et al. Single-layered organic photovoltaics with double cascading charge transport pathways: 18% efficiencies. Nat. Commun. 12, 309 (2021).

    Article  Google Scholar 

  4. 4.

    Hou, J., Inganäs, O., Friend, R. H. & Gao, F. Organic solar cells based on non-fullerene acceptors. Nat. Mater. 17, 119–128 (2018).

    Article  Google Scholar 

  5. 5.

    Menke, S. M., Ran, N. A., Bazan, G. C. & Friend, R. H. Understanding energy loss in organic solar cells: toward a new efficiency regime. Joule 2, 25–35 (2018).

    Article  Google Scholar 

  6. 6.

    Liu, X., Rand, B. P. & Forrest, S. R. Engineering charge-transfer states for efficient, low-energy-loss organic photovoltaics. Trends Chem. 1, 815–829 (2019).

    Google Scholar 

  7. 7.

    Vandewal, K., Tvingstedt, K., Gadisa, A., Inganäs, O. & Manca, J. V. On the origin of the open-circuit voltage of polymer–fullerene solar cells. Nat. Mater. 8, 904–909 (2009).

    Article  Google Scholar 

  8. 8.

    Benduhn, J. et al. Intrinsic non-radiative voltage losses in fullerene-based organic solar cells. Nat. Energy 2, 17053 (2017).

    Article  Google Scholar 

  9. 9.

    Qian, D. et al. Design rules for minimizing voltage losses in high-efficiency organic solar cells. Nat. Mater. 17, 703–709 (2018).

    Article  Google Scholar 

  10. 10.

    Eisner, F. D. et al. Hybridization of local exciton and charge-transfer states reduces nonradiative voltage losses in organic solar cells. J. Am. Chem. Soc. 141, 6362–6374 (2019).

    Article  Google Scholar 

  11. 11.

    Ran, N. A. et al. Impact of interfacial molecular orientation on radiative recombination and charge generation efficiency. Nat. Commun. 8, 79 (2017).

    Article  Google Scholar 

  12. 12.

    Liu, X., Li, Y., Ding, K. & Forrest, S. Energy loss in organic photovoltaics: nonfullerene versus fullerene acceptors. Phys. Rev. Appl. 11, 024060 (2019).

    Article  Google Scholar 

  13. 13.

    Ran, N. A. et al. Harvesting the full potential of photons with organic solar cells. Adv. Mater. 28, 1482–1488 (2016).

    Article  Google Scholar 

  14. 14.

    Liu, S. et al. High-efficiency organic solar cells with low non-radiative recombination loss and low energetic disorder. Nat. Photon. 14, 300–305 (2020).

    Google Scholar 

  15. 15.

    Green, M. A. Radiative efficiency of state-of-the-art photovoltaic cells. Prog. Photovolt. Res. Appl. 20, 472–476 (2012).

    Google Scholar 

  16. 16.

    Stranks, S. D. Nonradiative losses in metal halide perovskites. ACS Energy Lett. 2, 1515–1525 (2017).

    Article  Google Scholar 

  17. 17.

    Kirchartz, T., Rau, U., Kurth, M., Mattheis, J. & Werner, J. H. Comparative study of electroluminescence from Cu(In,Ga)Se2 and Si solar cells. Thin Solid Films 515, 6238 (2007).

    Article  Google Scholar 

  18. 18.

    Rau, U. Reciprocity relation between photovoltaic quantum efficiency and electroluminescent emission of solar cells. Phys. Rev. B 76, 085303 (2007).

    Article  Google Scholar 

  19. 19.

    Englman, R. & Jortner, J. The energy gap law for radiationless transitions in large molecules. Mol. Phys. 18, 145–164 (1970).

    Article  Google Scholar 

  20. 20.

    Ullbrich, S. et al. Emissive and charge-generating donor–acceptor interfaces for organic optoelectronics with low voltage losses. Nat. Mater. 18, 459 (2019).

    Article  Google Scholar 

  21. 21.

    Cui, Y. et al. Single-junction organic photovoltaic cells with approaching 18% efficiency. Adv. Mater. 32, 1908205 (2020).

    Article  Google Scholar 

  22. 22.

    Baran, D. et al. Reduced voltage losses yield 10% efficient fullerene free organic solar cells with >1 V open circuit voltages. Energy Environ. Sci. 9, 3783–3793 (2016).

    Article  Google Scholar 

  23. 23.

    Ziffer, M. E. et al. Long-lived, non-geminate, radiative recombination of photogenerated charges in a polymer/small-molecule acceptor photovoltaic blend. J. Am. Chem. Soc. 140, 9996–10008 (2018).

    Article  Google Scholar 

  24. 24.

    Karuthedath, S. et al. Intrinsic efficiency limits in low-bandgap non-fullerene acceptor organic solar cells. Nat. Mater. 20, 78–384 (2020).

  25. 25.

    Faist, M. A. et al. Competition between the charge transfer state and the singlet states of donor or acceptor limiting the efficiency in polymer:fullerene solar cells. J. Am. Chem. Soc. 134, 685–692 (2012).

    Article  Google Scholar 

  26. 26.

    Coffey, D. C. et al. An optimal driving force for converting excitons into free carriers in excitonic solar cells. J. Phys. Chem. C 116, 8916 (2012).

    Article  Google Scholar 

  27. 27.

    Vandewal, K. Interfacial charge transfer states in condensed phase systems. Annu. Rev. Phys. Chem. 67, 113–133 (2016).

    Article  Google Scholar 

  28. 28.

    Rand, B. P., Burk, D. P. & Forrest, S. R. Offset energies at organic semiconductor heterojunctions and their influence on the open-circuit voltage of thin-film solar cells. Phys. Rev. B 75, 115327 (2007).

    Article  Google Scholar 

  29. 29.

    Chen, X.-K., Coropceanu, V. & Brédas, J.-L. Assessing the nature of the charge-transfer electronic states in organic solar cells. Nat. Commun. 9, 5295 (2018).

    Article  Google Scholar 

  30. 30.

    Bixon, M., Jortner, J. & Verhoeven, J. W. Lifetimes for radiative charge recombination in donor-acceptor molecules. J. Am. Chem. Soc. 116, 7349–7355 (1994).

    Article  Google Scholar 

  31. 31.

    Fu, Y.-T. et al. Structure and disorder in squaraine–C60 organic solar cells: a theoretical description of molecular packing and electronic coupling at the donor–acceptor interface. Adv. Funct. Mater. 24, 3790–3798 (2014).

    Google Scholar 

  32. 32.

    Han, G., Guo, Y., Ma, X. & Yi, Y. Atomistic insight into donor/acceptor interfaces in high-efficiency nonfullerene organic solar cells. Sol. RRL 2, 1800190 (2018).

    Article  Google Scholar 

  33. 33.

    Zheng, Z., Tummala, N. R., Wang, T., Coropceanu, V. & Brédas, J.-L. Charge-transfer states at organic–organic interfaces: impact of static and dynamic disorders. Adv. Energy Mater. 9, 1803926 (2019).

    Article  Google Scholar 

  34. 34.

    Zheng, Z., Tummala, N. R., Fu, Y.-T., Coropceanu, V. & Brédas, J.-L. Charge-transfer states in organic solar cells: understanding the impact of polarization, delocalization, and disorder. ACS Appl. Mater. Interfaces 9, 18095 (2017).

    Article  Google Scholar 

  35. 35.

    Wang, T. & Brédas, J.-L. Organic solar cells based on non-fullerene small-molecule acceptors: impact of substituent position. Matter 2, 119–135 (2020).

    Google Scholar 

  36. 36.

    Vollbrecht, J. et al. Quantifying the nongeminate recombination dynamics in nonfullerene bulk heterojunction organic solar cells. Adv. Energy Mater. 9, 1901438 (2019).

    Article  Google Scholar 

  37. 37.

    Reinhardt, J., Grein, M., Bühler, C., Schubert, M. & Würfel, U. Identifying the impact of surface recombination at electrodes in organic solar cells by means of electroluminescence and modeling. Adv. Energy Mater. 4, 1400081 (2014).

    Article  Google Scholar 

  38. 38.

    Panhans, M. et al. Molecular vibrations reduce the maximum achievable photovoltage in organic solar cells. Nat. Commun. 11, 1488 (2020).

    Article  Google Scholar 

  39. 39.

    Kirchartz, T., Kaienburg, P. & Baran, D. Figures of merit guiding research on organic solar cells. J. Phys. Chem. C 122, 5829–5843 (2018).

    Article  Google Scholar 

  40. 40.

    Coropceanu, V., Chen, X.-K., Wang, T., Zheng, Z. & Brédas, J.-L. Charge-transfer electronic states in organic solar cells. Nat. Rev. Mater. 4, 689 (2019).

    Article  Google Scholar 

  41. 41.

    Zampetti, A., Minotto, A. & Cacialli, F. Near-infrared (NIR) organic light-emitting diodes (OLEDs): challenges and opportunities. Adv. Funct. Mater. 29, 1807623 (2019).

    Article  Google Scholar 

  42. 42.

    Kim, D.-H. et al. High-efficiency electroluminescence and amplified spontaneous emission from a thermally activated delayed fluorescent near-infrared emitter. Nat. Photon. 12, 98–104 (2018).

    Article  Google Scholar 

  43. 43.

    Ai, X. et al. Efficient radical-based light-emitting diodes with doublet emission. Nature 563, 536–540 (2018).

    Article  Google Scholar 

  44. 44.

    Goushi, K., Yoshida, K., Sato, K. & Adachi, C. Organic light-emitting diodes employing efficient reverse intersystem crossing for triplet-to-singlet state conversion. Nat. Photon. 6, 253–258 (2012).

    Article  Google Scholar 

  45. 45.

    Miller, O. D., Yablonovitch, E. & Kurtz, S. R. Strong internal and external luminescence as solar cells approach the Shockley–Queisser limit. IEEE J. Photovolt. 2, 303–311 (2012).

    Article  Google Scholar 

  46. 46.

    Pazos-Outón, L. M. et al. Photon recycling in lead iodide perovskite solar cells. Science 351, 1430–1433 (2016).

    Article  Google Scholar 

  47. 47.

    Yablonovitch, E. Lead halides join the top optoelectronic league. Science 351, aaf4603 (2016).

    Article  Google Scholar 

  48. 48.

    Perdigón-Toro, L. et al. Barrierless free charge generation in the high-performance pm6:y6 bulk heterojunction non-fullerene solar cell. Adv. Mater. 32, 1906763 (2020).

    Article  Google Scholar 

  49. 49.

    Karki, A. et al. Understanding the high performance of over 15% efficiency in single-junction bulk heterojunction organic solar cells. Adv. Mater. 31, 1903868 (2019).

    Article  Google Scholar 

  50. 50.

    Zhong, Y. et al. Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers. Nat. Commun. 11, 833 (2020).

    Article  Google Scholar 

  51. 51.

    Yao, H. et al. 14.7% Efficiency organic photovoltaic cells enabled by active materials with a large electrostatic potential difference. J. Am. Chem. Soc. 141, 7743–7750 (2019).

    Google Scholar 

  52. 52.

    Hinrichsen, T. F. et al. Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells. Nat. Commun. 11, 5617 (2020).

    Article  Google Scholar 

  53. 53.

    Classen, A. et al. The role of exciton lifetime for charge generation in organic solar cells at negligible energy-level offsets. Nat. Energy 5, 711–719 (2020).

    Article  Google Scholar 

  54. 54.

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

    Article  Google Scholar 

  55. 55.

    Cheng, P. & Yang, Y. Narrowing the band gap: the key to high-performance organic photovoltaics. Acc. Chem. Res. 53, 1218–1228 (2020).

    Google Scholar 

  56. 56.

    Kahle, F.-J., Rudnick, A., Bässler, H. & Köhler, A. How to interpret absorption and fluorescence spectra of charge transfer states in an organic solar cell. Mater. Horiz. 5, 837–848 (2018).

    Article  Google Scholar 

  57. 57.

    Creutz, C., Newton, M. D. & Sutin, N. Metal–ligand and metal–metal coupling elements. J. Photochem. Photobiol. A 82, 47–59 (1994).

    Article  Google Scholar 

  58. 58.

    Xie, Y. et al. Assessing the energy offset at the electron donor/acceptor interface in organic solar cells through radiative efficiency measurements. Energy Environ. Sci. 12, 3556–3566 (2019).

    Google Scholar 

  59. 59.

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

    Google Scholar 

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We thank K. Vandewal (Hasselt University) for insightful discussions and H. Wu (South China University of Technology) for providing the EQEEL value in a Y11 neat film. The research in Linköping was supported by the Swedish Strategic Research Foundation through a Future Research Leader program to F.G. (FFL 18-0322), Swedish Research Council VR (grant nos. 2016-06146, 2018-06048 and 2019-00677), and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (faculty grant no. SFO-Mat-LiU #2009-00971); the work at Arizona was funded by the Department of the Navy, Office of Naval Research, under award no. N00014-20-1-2110 and the University of Arizona. F.G. is a Wallenberg Academy Fellow and O.I. is a Wallenberg Academy Scholar.

Author information




X.-K.C., D.Q., V.C., J.L.B. and F.G. conceived the project; X.-K.C. carried out all of the theoretical simulations. D.Q. developed new blends. D.Q. made the devices and conducted the spectroscopy measurements together with Y.W. T. K. and M.H. contributed to the measurements of the electroluminescence spectra. T.K., W.T., O.I., V.C., J.L.B. and F.G. contributed to the result analysis. D.Q. and J. Y. conducted the cyclic voltammetry measurements. H.Y., J.Y., M.Z., Y.Z., Y.L. and J.H. developed the donor and acceptor materials. Y.S. developed two of PBDT-TS1-based blends. X.-K.C., D.Q., V.C., J.L.B. and F.G. wrote the manuscript. F.G. supervised the project. All authors discussed the results and commented on the final manuscript.

Corresponding authors

Correspondence to Deping Qian, Veaceslav Coropceanu, Jean-Luc Bredas or Feng Gao.

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Supplementary Information

Supplementary Figs. 1–17, Notes 1–8 and Tables 1–8.

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Chen, XK., Qian, D., Wang, Y. et al. A unified description of non-radiative voltage losses in organic solar cells. Nat Energy 6, 799–806 (2021).

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