Block copolymers as efficient cathode interlayer materials for organic solar cells


Emerging needs for the large-scale industrialization of organic solar cells require high performance cathode interlayers to facilitate the charge extraction from organic semiconductors. In addition to improving the efficiency, stability and processability issues are major challenges. Herein, we design block copolymers with well controlled chemical composition and molecular weight for cathode interlayer applications. The block copolymer coated cathodes display high optical transmittance and low work function. Conductivity studies reveal that the block copolymer thin film has abundant conductive channels and excellent longitudinal electron conductivity due to the interpenetrating networks formed by the polymer blocks. Applications of the cathode interlayers in organic solar cells provide higher power conversion efficiency and better stability compared to the most widely-applied ZnO counterparts. Furthermore, no post-treatment is needed which enables excellent processability of the block copolymer based cathode interlayer.

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


  1. 1.

    Zhao J, Li Y, Yang G, Jiang K, Lin H, Ade H, Ma W, Yan H. Efficient organic solar cells processed from hydrocarbon solvents. Nature Energy, 2016, 1(2): 1–7

    Article  Google Scholar 

  2. 2.

    Hou J, Inganäs O, Friend R H, Gao F. Organic solar cells based on non-fullerene acceptors. Nature Materials, 2018, 17(2): 119–128

    CAS  Article  Google Scholar 

  3. 3.

    Chen H, Hu D, Yang Q, Gao J, Fu J, Yang K, He H, Chen S, Kan Z, Duan T, et al. All-small-molecule organic solar cells with an ordered liquid crystalline donor. Joule, 2019, 3(12): 3034–3047

    CAS  Article  Google Scholar 

  4. 4.

    Lee W, Jeong S, Lee C, Han G, Cho C, Lee J Y, Kim B J. Organic photovoltaics: self-organization of polymer additive, poly(2-vinylpyridine) via one-step solution processing to enhance the efficiency and stability of polymer solar cells. Advanced Energy Materials, 2017, 7(17): 1602812

    Article  Google Scholar 

  5. 5.

    Yang K, Fu J, Hu L, Xiong Z, Li M, Wei X, Xiao Z, Lu S, Sun K. Impact of ZnO photoluminescence on organic photovoltaic performance. ACS Applied Materials & Interfaces, 2018, 10(46): 39962–39969

    CAS  Article  Google Scholar 

  6. 6.

    Seh Z W, Fredrickson K D, Anasori B, Kibsgaard J, Strickler A L, Lukatskaya M R, Gogotsi Y, Jaramillo T F, Vojvodic A. Two-dimensional molybdenum carbide (MXene) as an efficient electrocatalyst for hydrogen evolution. ACS Energy Letters, 2016, 1(3): 589–594

    CAS  Article  Google Scholar 

  7. 7.

    Zhang X, Johansson E M. Reduction of charge recombination in PbS colloidal quantum dot solar cells at the quantum dot/ZnO interface by inserting a MgZnO buffer layer. Journal of Materials Chemistry. A, Materials for Energy and Sustainability, 2017, 5(1): 303–310

    CAS  Article  Google Scholar 

  8. 8.

    You J, Meng L, Song T B, Guo T F, Yang Y M, Chang W H, Hong Z, Chen H, Zhou H, Chen Q, et al. Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers. Nature Nanotechnology, 2016, 11(1): 75–81

    Article  Google Scholar 

  9. 9.

    Small C E, Chen S, Subbiah J, Amb C M, Tsang S W, Lai T H, Reynolds J R, So F. High-efficiency inverted dithienogermole-thienopyrrolodione-based polymer solar cells. Nature Photonics, 2012, 6(2): 115–120

    CAS  Article  Google Scholar 

  10. 10.

    Nian L, Zhang W, Zhu N, Liu L, Xie Z, Wu H, Würthner F, Ma Y. Photoconductive cathode interlayer for highly efficient inverted polymer solar cells. Journal of the American Chemical Society, 2015, 137(22): 6995–6998

    CAS  Article  Google Scholar 

  11. 11.

    Tan W Y, Wang R, Li M, Liu G, Chen P, Li X C, Lu S M, Zhu H L, Peng Q M, Zhu X H, et al. Lending triarylphosphine oxide to phenanthroline: a facile approach to high-performance organic small-molecule cathode interfacial material for organic photovoltaics utilizing air-stable cathodes. Advanced Functional Materials, 2014, 24(41): 6540–6547

    CAS  Article  Google Scholar 

  12. 12.

    Li M, Gao K, Wan X, Zhang Q, Kan B, Xia R, Liu F, Yang X, Feng H, Ni W, et al. Solution-processed organic tandem solar cells with power conversion efficiencies >12%. Nature Photonics, 2017, 11 (2): 85–90

    CAS  Article  Google Scholar 

  13. 13.

    Zhang Q, Kan B, Liu F, Long G, Wan X, Chen X, Zuo Y, Ni W, Zhang H, Li M, et al. Small-molecule solar cells with efficiency over 9%. Nature Photonics, 2015, 9(1): 35–41

    CAS  Article  Google Scholar 

  14. 14.

    He Z, Xiao B, Liu F, Wu H, Yang Y, Xiao S, Wang C, Russell T P, Cao Y. Single-junction polymer solar cells with high efficiency and photovoltage. Nature Photonics, 2015, 9(3): 174–179

    CAS  Article  Google Scholar 

  15. 15.

    Yang B, Zhang S, Li S, Yao H, Li W, Hou J. A self-organized poly (vinylpyrrolidone)-based cathode interlayer in inverted fullerenefree organic solar cells. Advanced Materials, 2019, 31(2): 1804657

    Article  Google Scholar 

  16. 16.

    Zhou Y, Fuentes-Hernandez C, Shim J, Meyer J, Giordano A J, Li H, Winget P, Papadopoulos T, Cheun H, Kim J, et al. A universal method to produce low-work function electrodes for organic electronics. Science, 2012, 336(6079): 327–332

    CAS  Article  Google Scholar 

  17. 17.

    Zhou H, Chen Q, Li G, Luo S, Song T B, Duan H S, Hong Z, You J, Liu Y, Yang Y. Interface engineering of highly efficient perovskite solar cells. Science, 2014, 345(6196): 542–546

    CAS  Article  Google Scholar 

  18. 18.

    Ge J, Yin Y. Responsive photonic crystals. Angewandte Chemie International Edition, 2011, 50(7): 1492–1522

    CAS  Article  Google Scholar 

  19. 19.

    Hawker C J, Bosman A W, Harth E. New polymer synthesis by nitroxide mediated living radical polymerizations. Chemical Reviews, 2001, 101(12): 3661–3688

    CAS  Article  Google Scholar 

  20. 20.

    Hawker C J. Molecular weight control by a “living” free-radical polymerization process. Journal of the American Chemical Society, 1994, 116(24): 11185–11186

    CAS  Article  Google Scholar 

  21. 21.

    Zhang C, Bates M W, Geng Z, Levi A E, Vigil D, Barbon S M, Loman T, Delaney K T, Fredrickson G H, Bates C M, et al. Rapid generation of block copolymer libraries using automated chromatographic separation. Journal of the American Chemical Society, 2020, 142(21): 9843–9849

    CAS  PubMed  Google Scholar 

  22. 22.

    Cai W, Xu D, Qian L, Wei J, Xiao C, Qian L, Lu Z Y, Cui S. Force-induced transition of p-p stacking in a single polystyrene chain. Journal of the American Chemical Society, 2019, 141(24): 9500–9503

    CAS  Article  Google Scholar 

  23. 23.

    Holzwarth U, Gibson N. The Scherrer equation versus the ‘Debye-Scherrer equation’. Nature Nanotechnology, 2011, 6(9): 534–534

    CAS  Article  Google Scholar 

  24. 24.

    Hu L, Fu J, Yang K, Xiong Z, Wang M, Yang B, Wang H, Tang X, Zang Z, Li M, et al. Inhibition of in-plane charge transport in hole transfer layer to achieve high fill factor for inverted planar perovskite solar cells. Solar RRL, 2019, 3(7): 1900104

    Article  Google Scholar 

  25. 25.

    Li W, Ye L, Li S, Yao H, Ade H, Hou J. A high-efficiency organic solar cell enabled by the strong intramolecular electron push-pull effect of the nonfullerene acceptor. Advanced Materials, 2018, 30 (16): 1707170

    Article  Google Scholar 

  26. 26.

    Li G, Shrotriya V, Huang J, Yao Y, Moriarty T, Emery K, Yang Y. High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends. Nature Materials, 2005, (11): 864–868

  27. 27.

    Aqoma H, Park S, Park H Y, Hadmojo W T, Oh S H, Nho S, Kim D H, Seo J, Park S, Ryu D Y, et al. 11 % organic photovoltaic devices based on PTB7-Th: PC71BM photoactive layers and irradiationassisted ZnO electron transport layers. Advancement of Science, 2018, 5(7): 1700858

    Google Scholar 

  28. 28.

    Azmi R, Hadmojo W T, Sinaga S, Lee C L, Yoon S C, Jung I H, Jang S Y. High-efficiency low-temperature ZnO based perovskite solar cells based on highly polar, nonwetting self-assembled molecular layers. Advanced Energy Materials, 2018, 8(5): 1701683

    Article  Google Scholar 

  29. 29.

    Sun Y, Seo J H, Takacs C J, Seifter J, Heeger A J. Inverted polymer solar cells integrated with a low-temperature-annealed sol-gel-derived ZnO film as an electron transport layer. Advanced Materials, 2011, 23(14): 1679–1683

    CAS  Article  Google Scholar 

  30. 30.

    Fu J, Chen S, Yang K, Jung S, Lv J, Lan L, Chen H, Hu D, Yang Q, Duan T, et al. A “-hole” containing volatile solid additive enabling 16.5% efficiency organic solar cells. iScience, 2020, 23(3): 100965

    CAS  Article  Google Scholar 

  31. 31.

    Dong X, Yang K, Tang H, Hu D, Chen S, Zhang J, Kan Z, Duan T, Hu C, Dai X, et al. Improving molecular planarity by changing alky chain position enables 12.3% efficiency all-small-molecule organic solar cells with enhanced carrier lifetime and reduced recombination. Solar RRL, 2020, 4(1): 1900326

    CAS  Article  Google Scholar 

Download references


This work was financially supported by research grants from the National Natural Science Foundation of China (Grant Nos. 21801238 and 61504015), National Youth Thousand Program Project (Grant No. R52A199Z11), CAS Pioneer Hundred Talents Program B (Grant No. Y92A010Q10), National Special Funds for Repairing and Purchasing Scientific Institutions (Grant No. Y72Z090Q10), the Natural Science Foundation of Chongqing (Grant Nos. cstc2017jcyjA0752, cstc2018jcy-jAX0556, cstc2017jcy-jAX0384, and cstc2018jszx-cyzdX0137), the “artificial intelligence” key project of Chongqing (Grant No. cstc2017rgznzdyfX0030), the Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Grant Nos. LLEUTS-2017004, LLEUTS-2019001), the Venture & Innovation Support Program for Chongqing Overseas Returnees (Grant Nos. cx2017034 and cx2019028), Chongqing Talents Top Youth Talent Program (Grant No. CQYC201905057).

Author information



Corresponding authors

Correspondence to Shirong Lu or Kuan Sun or Zeyun Xiao.

Electronic supplementary material

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Hu, D., Fu, J., Chen, S. et al. Block copolymers as efficient cathode interlayer materials for organic solar cells. Front. Chem. Sci. Eng. (2021).

Download citation


  • organic solar cell
  • block copolymer
  • cathode interlayer