Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Efficient inverted polymer solar cells employing favourable molecular orientation

Nature Photonics volume 9, pages 403–408 (2015)Cite this article

Subjects

Abstract

Improving the power conversion efficiency of polymer-based bulk-heterojunction solar cells is a critical issue. Here, we show that high efficiencies of ∼10% can be obtained using the crystalline polymer PNTz4T in single-junction inverted cells with a thick active layer having a thickness of ∼300 nm. The improved performance is probably due to the large population of polymer crystallites with a face-on orientation and the ‘favourable’ distribution of edge-on and face-on crystallites along the film thickness (revealed by in-depth studies of the blend films using grazing-incidence wide-angle X-ray diffraction), which results in a reduction in charge recombination and efficient charge transport. These results underscore the great promise of polymer solar cells and raise the hope of achieving even higher efficiencies by means of materials development and control of molecular ordering.

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

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Figure 1
Figure 2: Photovoltaic characteristics of PNTz4T-based cells with conventional and inverted architectures.
Figure 3: GIWAXD data for PNTz4T/PC61BM blend films.
Figure 4: Schematic illustrations of PNTz4T/PC61BM blend films in the PSCs.

Similar content being viewed by others

References

  1. Yu, G., Gao, J., Hummelen, J. C., Wudl, F. & Heeger, A. J. Polymer photovoltaic cells: enhanced efficiencies via a network of internal donor–acceptor heterojunctions. Science 270, 1789–1791 (1995).

    Article  ADS  Google Scholar 

  2. Günes, S., Neugebauer, H. & Sariciftci, N. S. Conjugated polymer-based organic solar cells. Chem. Rev. 107, 1324–1338 (2007).

    Article  Google Scholar 

  3. Brabec, C., Dyakonov, V. & Scherf, U. Organic Photovoltaics: Materials, Device Physics, and Manufacturing Technologies (Wiley-VCH, 2008).

    Book  Google Scholar 

  4. He, Z. et al. Enhanced power-conversion efficiency in polymer solar cells using an inverted device structure. Nature Photon. 6, 591–595 (2012).

    Article  ADS  Google Scholar 

  5. Ye, L., Zhang, S., Zhao, W., Yao, H. & Hou, J. Highly efficient 2D-conjugated benzodithiophene-based photovoltaic polymer with linear alkylthio side chain. Chem. Mater. 26, 3603–3605 (2014).

    Article  Google Scholar 

  6. Liao, S.-H. et al. Single junction inverted polymer solar cell reaching power conversion efficiency 10.31% by employing dual-doped zinc oxide nano-film as cathode interlayer. Sci. Rep. 4, 6813 (2014).

    Article  Google Scholar 

  7. Liu, Y. et al. Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells. Nature Commun. 5, 5293 (2014).

    Article  ADS  Google Scholar 

  8. You, J. et al. A polymer tandem solar cell with 10.6% power conversion efficiency. Nature Commun. 4, 1446 (2013).

    Article  ADS  Google Scholar 

  9. You, J. et al. 10.2% power conversion efficiency polymer tandem solar cells consisting of two identical sub-cells. Adv. Mater. 25, 3973–3978 (2013).

    Article  Google Scholar 

  10. Scharber, M. C. et al. Design rules for donors in bulk-heterojunction solar cells—towards 10% energy-conversion efficiency. Adv. Mater. 18, 789–794 (2006).

    Article  Google Scholar 

  11. Facchetti, A. π-Conjugated polymers for organic electronics and photovoltaic cell applications. Chem. Mater. 23, 733–758 (2011).

    Article  Google Scholar 

  12. Boudreault, P.-L. T., Najari, A. & Leclerc, M. Processable low-bandgap polymers for photovoltaic applications. Chem. Mater. 23, 456–469 (2011).

    Article  Google Scholar 

  13. Beaujuge, P. M. & Fréchet, J. M. J. Molecular design and ordering effects in π-functional materials for transistor and solar cell applications. J. Am. Chem. Soc. 133, 20009–20029 (2011).

    Article  Google Scholar 

  14. Mühlbacher, D. et al. High photovoltaic performance of a low-bandgap polymer. Adv. Mater. 18, 2884–2889 (2006).

    Article  Google Scholar 

  15. Peet, J. et al. Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols. Nature Mater. 6, 497–500 (2007).

    Article  ADS  Google Scholar 

  16. Blouin, N. et al. Toward a rational design of poly(2, 7-carbazole) derivatives for solar cells. J. Am. Chem. Soc. 130, 732–742 (2008).

    Article  Google Scholar 

  17. Park, S. H. et al. Bulk heterojunction solar cells with internal quantum efficiency approaching 100%. Nature Photon. 3, 297–302 (2009).

    Article  ADS  Google Scholar 

  18. Liang, Y. et al. Development of new semiconducting polymers for high performance solar cells. J. Am. Chem. Soc. 131, 56–57 (2009).

    Article  Google Scholar 

  19. Liang, Y. et al. Highly efficient solar cell polymers developed via fine-tuning of structural and electronic properties. J. Am. Chem. Soc. 131, 7792–7799 (2009).

    Article  Google Scholar 

  20. Liang, Y. et al. For the bright future—bulk heterojunction polymer solar cells with power conversion efficiency of 7.4%. Adv. Mater. 22, E135–E138 (2010).

    Article  Google Scholar 

  21. Mataka, S. et al. Sulfur nitride in organic chemsitry. XIV, Selective formation of benzo-and benzobis[1, 2, 5]thiadiazole skeleton in the reaction of tetrasulfur tetranitride with naphthalenols and related compounds. Bull. Chem. Soc. Jpn 64, 68–73 (1991).

    Article  Google Scholar 

  22. Wang, M. et al. A donor–acceptor conjugated polymer based on naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole for high performance polymer solar cells. J. Am. Chem. Soc. 133, 9638–9641 (2011).

    Article  Google Scholar 

  23. Osaka, I. et al. Synthesis, characterization, and transistor and solar cell applications of a naphthobisthiadiazole-based semiconducting polymer. J. Am. Chem. Soc. 134, 3498–3507 (2012).

    Article  Google Scholar 

  24. Szarko, J. M. et al. When function follows form: effects of donor copolymer side chains on film morphology and BHJ solar cell performance. Adv. Mater. 22, 5468–5472 (2010).

    Article  Google Scholar 

  25. Guo, X. et al. Bithiopheneimide–dithienosilole/dithienogermole copolymers for efficient solar cells: information from structure–property–device performance correlations and comparison to thieno[3,4-c]pyrrole-4,6-dione analogues. J. Am. Chem. Soc. 134, 18427–18439 (2012).

    Article  Google Scholar 

  26. Peet, J. et al. Bulk heterojunction solar cells with thick active layers and high fill factors enabled by a bithiophene-co-thiazolothiazole push–pull copolymer. Appl. Phys. Lett. 98, 043301 (2011).

    Article  ADS  Google Scholar 

  27. Price, S. C., Stuart, A. C., Yang, L., Zhou, H. & You, W. Fluorine substituted conjugated polymer of medium band gap yields 7% efficiency in polymer–fullerene solar cells. J. Am. Chem. Soc. 133, 4625–4631 (2011).

    Article  Google Scholar 

  28. Li, W. et al. Efficient small bandgap polymer solar cells with high fill factors for 300 nm thick films. Adv. Mater. 3182–3186 (2013).

  29. Osaka, I., Kakara, T., Takemura, N., Koganezawa, T. & Takimiya, K. Naphthodithiophene–naphthobisthiadiazole copolymers for solar cells: alkylation drives the polymer backbone flat and promotes efficiency. J. Am. Chem. Soc. 135, 8834–8837 (2013).

    Article  Google Scholar 

  30. Osaka, I., Saito, M., Koganezawa, T. & Takimiya, K. Thiophene–thiazolothiazole copolymers: significant impact of side chain composition on backbone orientation and solar cell performances. Adv. Mater. 26, 331–338 (2014).

    Article  Google Scholar 

  31. Xu, Z. et al. Vertical phase separation in poly(3-hexylthiophene): fullerene derivative blends and its advantage for inverted structure solar cells. Adv. Funct. Mater. 19, 1227–1234 (2009).

    Article  Google Scholar 

  32. Guo, X. et al. Polymer solar cells with enhanced fill factors. Nature Photon. 7, 825–833 (2013).

    Article  ADS  Google Scholar 

  33. Stuart, A. C. et al. Fluorine substituents reduce charge recombination and drive structure and morphology development in polymer solar cells. J. Am. Chem. Soc. 135, 1806–1815 (2013).

    Article  Google Scholar 

  34. Sirringhaus, H., Brown, P., Friend, R. & Nielsen, M. Two-dimensional charge transport in self-organized, high-mobility conjugated polymers. Nature 401, 685–688 (1999).

    Article  ADS  Google Scholar 

  35. Baker, J. L. et al. Quantification of thin film crystallographic orientation using X-ray diffraction with an area detector. Langmuir 26, 9146–9151 (2010).

    Article  Google Scholar 

  36. Rivnay, J., Mannsfeld, S. C. B., Miller, C. E., Salleo, A. & Toney, M. F. Quantitative determination of organic semiconductor microstructure from the molecular to device scale. Chem. Rev. 112, 5488–5519 (2012).

    Article  Google Scholar 

  37. Umeda, T., Kumaki, D. & Tokito, S. Surface-energy-dependent field-effect mobilities up to 1 cm2/Vs for polymer thin-film transistor. J. Appl. Phys. 105, 024516 (2009).

    Article  ADS  Google Scholar 

  38. Kline, R., McGehee, M. & Toney, M. Highly oriented crystals at the buried interface in polythiophene thin film transistors. Nature Mater. 5, 222–228 (2006).

    Article  ADS  Google Scholar 

  39. Duong, D. T., Toney, M. F. & Salleo, A. Role of confinement and aggregation in charge transport in semicrystalline polythiophene thin films. Phys. Rev. B 86, 205205 (2012).

    Article  ADS  Google Scholar 

  40. Shrotriya, V., Yao, Y., Li, G. & Yang, Y. Effect of self-organization in polymer/fullerene bulk heterojunctions on solar cell performance. Appl. Phys. Lett. 89, 063505 (2006).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

This research was supported by Grants-in-Aid for Scientific Research from The Ministry of Education, Culture, Sports, Science and Technology (MEXT) (nos. 24685030 and 23245041) and by Precursory Research for Embryonic Science and Technology from the Japan Science and Technology Agency. This work was partly supported by the Nanotechnology Platform Program of MEXT. Two-dimensional GIWAXD experiments were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI, proposal no. 2014A1530). The authors thank K. Tajima of CEMS, RIKEN, for helpful discussions regarding the fabrication of inverted cells and for the contact angle measurement, and K. Higashimine of the Center for Nano Materials and Technology, JAIST, for the EDS measurements. The authors thank Y. Hishikawa of the National Institute of Advanced Industrial Science and Technology (AIST) and H. Tobita of Japan Electrical Safety & Environment Technology Laboratories (JET) for technical discussions about the J–V measurements. The authors also thank Y. Hishikawa and A. Sasaki for measurement of the cell active area.

Author information

Author notes

  1. Varun Vohra

    Present address: Present address: Department of Engineering Science, Graduate School of Informatics and Engineering, The University of Electro-Communications (UEC), 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-8585, Japan,

Authors and Affiliations

  1. School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, 923-1292, Ishikawa, Japan

    Varun Vohra & Hideyuki Murata

  2. Emergent Molecular Function Research Group, RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Saitama, Japan

    Kazuaki Kawashima, Itaru Osaka & Kazuo Takimiya

  3. Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, 739-8527, Hiroshima, Japan

    Kazuaki Kawashima & Takeshi Kakara

  4. Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, 679-5198, Hyogo, Japan

    Tomoyuki Koganezawa

  5. Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, 102-0075, Tokyo, Japan

    Itaru Osaka

Authors
  1. Varun Vohra
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Kazuaki Kawashima
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Takeshi Kakara
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Tomoyuki Koganezawa
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Itaru Osaka
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Kazuo Takimiya
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. Hideyuki Murata
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

K.K. prepared the polymer sample. V.V. and I.O. conceived and designed the solar cell experiments. V.V. and K.K. fabricated the conventional cells and K.K. and T.Ka. fabricated the inverted cells. I.O. and T.Ko. conceived and designed the GIWAXD experiments, and K.K. and T.Ko. conducted them. V.V., K.K. and I.O. prepared the manuscript, and all authors discussed and commented on the manuscript. V.V., I.O., K.T. and H.M. directed the project.

Corresponding authors

Correspondence to Varun Vohra, Itaru Osaka, Kazuo Takimiya or Hideyuki Murata.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 3422 kb)

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Vohra, V., Kawashima, K., Kakara, T. et al. Efficient inverted polymer solar cells employing favourable molecular orientation. Nature Photon 9, 403–408 (2015). https://doi.org/10.1038/nphoton.2015.84

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nphoton.2015.84

This article is cited by

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing