Skip to main content

Optimized mixed phases to achieve improved performance of organic solar cells


In the three-phase (pure donor, pure acceptor, and mixed phases) morphologies of organic solar cells, the mixed phases produce an energy cascade that promotes the generation of free carriers. However, how to optimize the content of the mixed phases is a challenging problem. The authors proposed to control different content of mixed phases in DRTB-T and IDIC blends by additive and solvent vapor annealing (SVA). The authors first formed the largest extent amount of mixed phases by the additive cinene (2%) to inhibit the crystallization of DRTB-T and IDIC. And then, different amounts of mixed phases were achieved by further SVA for different times (from 0 to 50 s) to increase the content of pure DRTB-T and IDIC phases. The energetic offsets (ΔE) of pure and mixed phases gradually decrease from 0.529 to 0.477 eV for different content of mixed phases. When ΔE was 0.498 eV, the highest photocurrent density (Jsc) was obtained. The power conversion efficiency was increased from 3.23% (without any treatment) to 8.54%. Therefore, the authors demonstrated that the optimized content of the mixed phases is critical to device performance.

This is a preview of subscription content, access via your institution.

Figure 1
Figure 2
Figure 3
Table I
Figure 4


  1. 1.

    T.M. Clarke and J.R. Durrant: Charge photogeneration in organic solar cells. Chem. Rev. 110, 6736–6767 (2010).

    CAS  Article  Google Scholar 

  2. 2.

    M. Scarongella, J. De Jonghe-Risse, E. Buchaca-Domingo, M. Causa’, Z. Fei, M. Heeney, J.-E. Moser, N. Stingelin, and N. Banerji: A close look at charge generation in polymer: fullerene blends with microstruc-ture control. J. Am. Chem. Soc. 137, 2908–2918 (2015).

    CAS  Article  Google Scholar 

  3. 3.

    L. Yang, S. Zhang, C. He, J. Zhang, H. Yao, Y. Yang, Y. Zhang, W. Zhao, and J. Hou: New wide band gap donor for efficient fullerene-free all-small-molecule organic solar cells. J. Am. Chem. Soc. 139, 1958–1966 (2017).

    CAS  Article  Google Scholar 

  4. 4.

    Q. Zhang, Z. Chen, W. Ma, Z. Xie, J. Liu, X. Yu, and Y. Han: Efficient non-halogenated solvent-processed ternary all-polymer solar cells with a favorable morphology enabled by two well-compatible donors. ACS Appl. Mater. Interfaces 11, 32200–32208 (2019).

    CAS  Article  Google Scholar 

  5. 5.

    X. Cao, Q. Zhang, K. Zhou, X. Yu, J. Liu, Y. Han, and Z. Xie: Improve exciton generation and dissociation by increasing fullerene content in the mixed phase of P3HT/fullerene. Colloids Surf. A 506, 723–731 (2016).

    CAS  Article  Google Scholar 

  6. 6.

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

    CAS  Article  Google Scholar 

  7. 7.

    S. Holliday, Y. Li, and C.K. Luscombe: Recent advances in high performance donor-acceptor polymers for organic photovoltaics. Prog. Polym. Sci. 70, 34–51 (2017).

    CAS  Article  Google Scholar 

  8. 8.

    S. Sweetnam, K.R. Graham, G.O. Ngongang Ndjawa, T. Heumuller, J.A. Bartelt, T.M. Burke, W. Li, W. You, A. Amassian, and M.D. McGehee: Characterization of the polymer energy landscape in polymer: fullerene bulk heterojunctions with pure and mixed phases. J. Am. Chem. Soc. 136, 14078–14088 (2014).

    CAS  Article  Google Scholar 

  9. 9.

    P. Westacott, J.R. Tumbleston, S. Shoaee, S. Fearn, J.H. Bannock, J.B. Gilchrist, S. Heutz, J. deMello, M. Heeney, H. Ade, J. Durrant, D.S. McPhail, and N. Stingelin: On the role of intermixed phases in organic photovoltaic blends. Energy Environ. Sci. 6, 2756 (2013).

    CAS  Article  Google Scholar 

  10. 10.

    M. Pfannmoller, H. Flugge, G. Benner, I. Wacker, C. Sommer, M. Hanselmann, S. Schmale, H. Schmidt, F.A. Hamprecht, T. Rabe, W. Kowalsky, and R.R. Schroder: Visualizing a homogeneous blend in bulk heterojunction polymer solar cells by analytical electron microscopy. Nano Lett. 11, 3099–3107 (2011).

    CAS  Article  Google Scholar 

  11. 11.

    Q. Zhang, J. Liu, X. Yu, and Y. Han: Design optimized intermixed phase by tuning polymer-fullerene intercalation for free charge generation. Chin. Chem. Lett. 30, 140–1409 (2019).

    Google Scholar 

  12. 12.

    M. Osaka, H. Benten, H. Ohkita, and S. Ito: Intermixed donor/acceptor region in conjugated polymer blends visualized by conductive atomic force microscopy. Macromolecules 50, 1618–1625 (2017).

    CAS  Article  Google Scholar 

  13. 13.

    C. McDowell, M. Abdelsamie, M.F. Toney, and G.C. Bazan: Solvent additives: key morphology-directing agents for solution-processed organic solar cells. Adv. Mater (30), e1707114 (2018).

    Google Scholar 

  14. 14.

    F.C. Jamieson, E.B. Domingo, T. McCarthy-Ward, M. Heeney, N. Stingelin, and J.R. Durrant: Fullerene crystallisation as a key driver of charge separation in polymer/fullerene bulk heterojunction solar cells. Chem. Sci. 3, 48–492 (2012).

    Article  Google Scholar 

  15. 15.

    J.A. Bartelt, Z.M. Beiley, E.T. Hoke, W.R. Mateker, J.D. Douglas, B.A. Collins, J.R. Tumbleston, K.R. Graham, A. Amassian, H. Ade, J.M.J. Fréchet, M.F. Toney, and M.D. McGehee: The importance of fullerene percolation in the mixed regions of polymer-fullerene bulk heterojunction solar cells. Adv. Energy Mater. 3, 364–374 (2013).

    CAS  Article  Google Scholar 

  16. 16.

    C. Groves: Suppression of geminate charge recombination in organic photovoltaic devices with a cascaded energy heterojunction. Energy Environ. Sci. 6, 1546 (2013).

    CAS  Article  Google Scholar 

  17. 17.

    Y. Huang, E.J. Kramer, A.J. Heeger, and G.C. Bazan: Bulk heterojunction solar cells: morphology and performance relationships. Chem. Rev. 114, 7006–7043 (2014).

    CAS  Article  Google Scholar 

  18. 18.

    E. Buchaca-Domingo, A.J. Ferguson, F.C. Jamieson, T. McCarthy-Ward, S. Shoaee, J.R. Tumbleston, O.G. Reid, L. Yu, M.B. Madec, M. Pfannmöller, F. Hermerschmidt, R.R. Schröder, S.E. Watkins, N. Kopidakis, G. Portale, A. Amassian, M. Heeney, H. Ade, G. Rumbles, J. R. Durrant, and N. Stingelin: Additive-assisted supramolecular manipulation of polymer: fullerene blend phase morphologies and its influence on photophysical processes. Mater. Horiz. 1, 270–279 (2014).

    CAS  Article  Google Scholar 

  19. 19.

    B. Huang, J.A. Amonoo, A. Li, X.C. Chen, and P.F. Green: Role of domain size and phase purity on charge carrier density, mobility, and recombination in poly(3-hexylthiophene): phenyl-C61-butyric acid methyl ester devices. J. Phys. Chem. C 118, 3968–3975 (2014).

    CAS  Article  Google Scholar 

  20. 20.

    T.M. Burke and M.D. McGehee: How high local charge carrier mobility and an energy cascade in a three-phase bulk heterojunction enable >90% quantum efficiency. Adv. Mater. 26, 1923–1928 (2014).

    CAS  Article  Google Scholar 

  21. 21.

    W.C. Tsoi, S.J. Spencer, L. Yang, A.M. Ballantyne, P.G. Nicholson, A. Turnbull, A.G. Shard, C.E. Murphy, D.D.C. Bradley, J. Nelson, and J.-S. Kim: Effect of crystallization on the electronic energy levels and thin film morphology of P3HT:PCBM blends. Macromolecules 44, 2944–2952 (2011).

    CAS  Article  Google Scholar 

  22. 22.

    O. Alqahtani, M. Babics, J. Gorenflot, V. Savikhin, T. Ferron, A.H. Balawi, A. Paulke, Z. Kan, M. Pope, A.J. Clulow, J. Wolf, P.L. Burn, I.R. Gentle, D. Neher, M.F. Toney, F. Laquai, P.M. Beaujuge, and B.A. Collins: Mixed domains enhance charge generation and extraction in bulk-heterojunction solar cells with small-molecule donors. Adv. Energy Mater. 8, 1702941 (2018).

    Article  Google Scholar 

  23. 23.

    Q. Liang, J. Han, C. Song, Z. Wang, J. Xin, X. Yu, Z. Xie, W. Ma, J. Liu, and Y. Han: Tuning molecule diffusion to control the phase separation of the p-DTS(FBTTh2)2/EP-PDI blend system via thermal annealing. J. Mater. Chem. C 5, 6842–6851 (2017).

    CAS  Article  Google Scholar 

  24. 24.

    M. Li, Q. Liang, Q. Zhao, K. Zhou, X. Yu, Z. Xie, J. Liu, and Y. Han: A bi-continuous network structure of p-DTS(FBTTh2)2/EP-PDI via selective solvent vapor annealing. J. Mater. Chem. C 4, 1009–10104 (2016).

    Article  Google Scholar 

  25. 25.

    Y.-D. Liu, Q. Zhang, X.-H. Yu, J.-G. Liu, and Y.-C. Han: Increasing the content of β phase of poly(9,9-dioctylfluorene) by synergistically controlling solution aggregation and extending film-forming time. Chin. J. Polym. Sci. 37, 664–673 (2019).

    CAS  Article  Google Scholar 

  26. 26.

    H. Zhang, X. Wang, L. Yang, S. Zhang, Y. Zhang, C. He, W. Ma, and J. Hou: Improved domain size and purity enables efficient all-small-molecule ternary solar cells. Adv. Mater 29, 201703777 (2017).

    Google Scholar 

  27. 27.

    J. Liu, L. Chen, B. Gao, X. Cao, Y. Han, Z. Xie, and L. Wang: Constructing the nanointerpenetrating structure of PCDTBT:PC70BM bulk heterojunc-tion solar cells induced by aggregation of PC70BM via mixed-solvent vapor annealing. J. Mater. Chem. A 1, 6216 (2013).

    CAS  Article  Google Scholar 

  28. 28.

    L. Yang, S. Zhang, C. He, J. Zhang, Y. Yang, J. Zhu, Y. Cui, W. Zhao, H. Zhang, Y. Zhang, Z. Wei, and J. Hou: Modulating molecular orientation enables efficient nonfullerene small-molecule organic solar cells. Chem. Mater. 30, 2129–2134 (2018).

    CAS  Article  Google Scholar 

Download references


This work was supported by the National Natural Science Foundation of China (51890871, 91833306, and 51573185). W.M. thanks for the support from the Ministry of Science and Technology (No. 2016YFA0200700), NSFC (21875182), and 111 Projects 2.0 (BP2018008). X-ray data were acquired at beamlines 7.3.3 and at the Advanced Light Source, which is supported by the Director, Office of Science, Office of Basic Energy Sciences, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The authors thank Chenhui Zhu at beamline 7.3.3 and Cheng Wang at beamline for assistance with data acquisition.

Author information



Corresponding author

Correspondence to Yanchun Han.

Supplementary material

Supplementary material

The supplementary material for this article can be found at u]

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Yi, Y., Gao, X., Yuan, J. et al. Optimized mixed phases to achieve improved performance of organic solar cells. MRS Communications 9, 1235–1241 (2019).

Download citation