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Emissive and charge-generating donor–acceptor interfaces for organic optoelectronics with low voltage losses


Intermolecular charge-transfer states at the interface between electron donating (D) and accepting (A) materials are crucial for the operation of organic solar cells but can also be exploited for organic light-emitting diodes1,2. Non-radiative charge-transfer state decay is dominant in state-of-the-art D–A-based organic solar cells and is responsible for large voltage losses and relatively low power-conversion efficiencies as well as electroluminescence external quantum yields in the 0.01–0.0001% range3,4. In contrast, the electroluminescence external quantum yield reaches up to 16% in D–A-based organic light-emitting diodes5,6,7. Here, we show that proper control of charge-transfer state properties allows simultaneous occurrence of a high photovoltaic and emission quantum yield within a single, visible-light-emitting D–A system. This leads to ultralow-emission turn-on voltages as well as significantly reduced voltage losses upon solar illumination. These results unify the description of the electro-optical properties of charge-transfer states in organic optoelectronic devices and foster the use of organic D–A blends in energy conversion applications involving visible and ultraviolet photons8,9,10,11.

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Fig. 1: Studied material systems, reciprocity relation between CT absorption and emission, and current–voltage characteristics.
Fig. 2: Temperature-dependent Voc and the EL measurements.
Fig. 3: Open-circuit voltage and non-radiative voltage losses as a function of ECT.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.


  1. 1.

    Yan, C. et al. Non-fullerene acceptors for organic solar cells. Nat. Rev. Mater. 3, 18003 (2018).

    CAS  Article  Google Scholar 

  2. 2.

    Sarma, M. & Wong, K.-T. Exciplex: an intermolecular charge-transfer approach for TADF. ACS Appl. Mater. Interfaces 10, 19279–19304 (2018).

    CAS  Article  Google Scholar 

  3. 3.

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

    CAS  Article  Google Scholar 

  4. 4.

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

    CAS  Article  Google Scholar 

  5. 5.

    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).

    CAS  Article  Google Scholar 

  6. 6.

    Chen, D. et al. Fluorescent organic planar pn heterojunction light-emitting diodes with simplified structure, extremely low driving voltage, and high efficiency. Adv. Mater. 28, 239–244 (2016).

    Article  Google Scholar 

  7. 7.

    Lin, T.-C. et al. Probe exciplex structure of highly efficient thermally activated delayed fluorescence organic light emitting diodes. Nat. Commun. 9, 3111 (2018).

    Article  Google Scholar 

  8. 8.

    Davy, N. C. et al. Pairing of near-ultraviolet solar cells with electrochromic windows for smart management of the solar spectrum. Nat. Energy 2, 17104 (2017).

    CAS  Article  Google Scholar 

  9. 9.

    Lungenschmied, C. et al. Flexible, long-lived, large-area, organic solar cells. Sol. Energy Mater. Sol. Cells 91, 379–384 (2007).

    CAS  Article  Google Scholar 

  10. 10.

    Meerheim, R., Körner, C. & Leo, K. Highly efficient organic multi-junction solar cells with a thiophene based donor material. Appl. Phys. Lett. 105, 063306 (2014).

    Article  Google Scholar 

  11. 11.

    Meng, L. et al. Organic and solution-processed tandem solar cells with 17.3% efficiency. Science 6407, 1094–1098 (2018).

    Article  Google Scholar 

  12. 12.

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

    CAS  Article  Google Scholar 

  13. 13.

    Liu, X. K. et al. Prediction and design of efficient exciplex emitters for high-efficiency, thermally activated delayed-fluorescence organic light-emitting diodes. Adv. Mater. 27, 2378–2383 (2015).

    CAS  Article  Google Scholar 

  14. 14.

    Chang, W. et al. Spin-dependent charge transfer state design rules in organic photovoltaics. Nat. Commun. 6, 6415 (2015).

    Article  Google Scholar 

  15. 15.

    Attar, Aa. H. A. & Monkman, A. P. Electric field induce blue shift and intensity enhancement in 2D exciplex organic light emitting diodes; controlling electron–hole separation. Adv. Mater. 28, 8014–8020 (2016).

    Article  Google Scholar 

  16. 16.

    Jenekhe, S. A. & Osaheni, J. A. Excimers and exciplexes of conjugated polymers. Science 265, 765–768 (1994).

    CAS  Article  Google Scholar 

  17. 17.

    Vandewal, K. et al. Efficient charge generation by relaxed charge-transfer states at organic interfaces. Nat. Mater. 13, 63–68 (2014).

    CAS  Article  Google Scholar 

  18. 18.

    Park, S. H. et al. Bulk heterojunction solar cells with internal quantum efficiency approaching 100%. Nat. Photon. 3, 297–303 (2009).

    CAS  Article  Google Scholar 

  19. 19.

    Vandewal, K., Tvingstedt, K., Gadisa, A., Inganäs, O. & Manca, J. V. Relating the open-circuit voltage to interface molecular properties of donor:acceptor bulk heterojunction solar cells. Phys. Rev. B 81, 125204 (2010).

    Article  Google Scholar 

  20. 20.

    Tvingstedt, K. et al. Radiative efficiency of lead iodide based perovskite solar cells. Nat. Sci. Rep. 4, 6071 (2014).

    CAS  Article  Google Scholar 

  21. 21.

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

    Article  Google Scholar 

  22. 22.

    McNaught, A. D. & Wilkinson, A. IUPAC Compendium of Chemical Terminology 2nd edn (Blackwell Scientific, 1997).

  23. 23.

    Tvingstedt, K. & Deibel, C. Temperature dependence of ideality factors in organic solar cells and the relation to radiative efficiency. Adv. Energy Mater. 6, 1502230 (2016).

    Article  Google Scholar 

  24. 24.

    Banerjee, S. & Anderson, W. A. Temperature dependence of shunt resistance in photovoltaic devices. Appl. Phys. Lett. 49, 38–40 (1986).

    CAS  Article  Google Scholar 

  25. 25.

    Santos, Da. P. L., Dias, F. B. & Monkman, A. P. Investigation of the mechanisms giving rise to TADF in exciplex states. J. Phys. Chem. C 120, 18259–18267 (2016).

    Article  Google Scholar 

  26. 26.

    Yokoyama, D., Sasabe, H., Furukawa, Y., Adachi, C. & Kido, J. Molecular stacking induced by intermolecular C–HN hydrogen bonds leading to high carrier mobility in vacuum-deposited organic films. Adv. Funct. Mater. 21, 1375–1382 (2011).

    CAS  Article  Google Scholar 

  27. 27.

    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 

  28. 28.

    Liu, X. et al. Efficient organic solar cells with extremely high open-circuit voltages and low voltage losses by suppressing nonradiative recombination losses. Adv. Energy Mater. 9, 1801699 (2018).

    Article  Google Scholar 

  29. 29.

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

    CAS  Article  Google Scholar 

  30. 30.

    Azzouzi, M. et al. Nonradiative energy losses in bulk-heterojunction organic photovoltaics. Phys. Rev. X 8, 31055 (2018).

    CAS  Google Scholar 

  31. 31.

    Kayes, B. M. et al. 27.6% conversion efficiency, a new record for single-junction solar cells under 1 sun illumination. In IEEE Photovoltaic Specialists Conference (IEEE, 2011).

  32. 32.

    Zhang, J. et al. Efficient non-fullerene organic solar cells employing sequentially deposited donor–acceptor layers. J. Mater. Chem. A 6, 18225–18233 (2018).

    CAS  Article  Google Scholar 

  33. 33.

    Yang, D. et al. A minimal non-radiative recombination loss for efficient non-fullerene all-small-molecule organic solar cells with a low energy loss of 0.54 eV and high open-circuit voltage of 1.15 V. J. Mater. Chem. A 6, 13918–13924 (2018).

    CAS  Article  Google Scholar 

  34. 34.

    Tang, Z. et al. A new fullerene-free bulk-heterojunction system for efficient high-voltage and high-fill factor solution-processed organic photovoltaics. Adv. Mater. 27, 1900–1907 (2015).

    CAS  Article  Google Scholar 

  35. 35.

    Nikolis, V. C. et al. Reducing voltage losses in cascade organic solar cells while maintaining high external quantum efficiencies. Adv. Energy Mater. 7, 1700855 (2017).

    Article  Google Scholar 

  36. 36.

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

    CAS  Article  Google Scholar 

  37. 37.

    Benduhn, J. et al. Impact of triplet excited states on the open-circuit voltage of organic solar cells. Adv. Energy Mater. 8, 1800451 (2018).

    Article  Google Scholar 

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This work was supported by the German Federal Ministry for Education and Research (BMBF) through the InnoProfile project ‘Organische p–i–n Bauelemente 2.2’ (03IPT602X) and by the German Research Foundation (DFG) project Photogen (VA 1035/5-1). X.J. and Y.L. acknowledge support from the China Scholarship Council (nos. 201706140127 and 201506920047, respectively). The authors also acknowledge the DFG for supporting K.T. (project 382633022 ‘RECOLPER’), F.P., S.Ro. and D.N. (SFB 951 ‘HIOS’) and A.F. (RE 3198/6-1 ‘EFOD’).

Author information




S.U., J.B., X.J., D.S. and K.V. designed the experiments, prepared photovoltaic devices and optimized their processing parameters for photovoltaic performance. S.U., X.J., Y.L. and J.W. performed temperature-dependent characterization of the devices. J.B. and X.J. measured the sensitive EQEPV spectra. K.T., V.C.N., F.P. and S.Ro. measured the EQEEL and corresponding electroluminescence spectra. D.N., A.F., S.Re. and K.V. supervised sub-tasks (OPV and OLED design, investigation and data interpretation) within the project and participated in discussions of the findings. K.V. supervised the overall project. All authors contributed to the data analysis and writing of the manuscript.

Corresponding authors

Correspondence to Sascha Ullbrich or Johannes Benduhn or Koen Vandewal.

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Supplementary Information

Supplementary Tables 1–5, Supplementary Figures 1–8, Supplementary References 1–35

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Ullbrich, S., Benduhn, J., Jia, X. et al. Emissive and charge-generating donor–acceptor interfaces for organic optoelectronics with low voltage losses. Nat. Mater. 18, 459–464 (2019).

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