Letter | Published:

Highly efficient photocathodes for dye-sensitized tandem solar cells

Nature Materials volume 9, pages 3135 (2010) | Download Citation



Thin-film dye-sensitized solar cells (DSCs) based on mesoporous semiconductor electrodes are low-cost alternatives to conventional silicon devices1,2. High-efficiency DSCs typically operate as photoanodes (n-DSCs), where photocurrents result from dye-sensitized electron injection into n-type semiconductors. Dye-sensitized photocathodes (p-DSCs) operate in an inverse mode, where dye-excitation is followed by rapid electron transfer from a p-type semiconductor to the dye (dye-sensitized hole injection). Such p-DSCs and n-DSCs can be combined to construct tandem solar cells3 (pn-DSCs) with a theoretical efficiency limitation well beyond that of single-junction DSCs (ref. 4). Nevertheless, the efficiencies of such tandem pn-DSCs have so far been hampered by the poor performance of the available p-DSCs (refs 3, 5–15). Here we show for the first time that p-DSCs can convert absorbed photons to electrons with yields of up to 96%, resulting in a sevenfold increase in energy conversion efficiency compared with previously reported photocathodes7. The donor–acceptor dyes, studied as photocathodic sensitizers, comprise a variable-length oligothiophene bridge, which provides control over the spatial separation of the photogenerated charge carriers. As a result, charge recombination is decelerated by several orders of magnitude and tandem pn-DSCs can be constructed that exceed the efficiency of their individual components.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1.

    & A low-cost, high-efficiency solar-cell based on dye-sensitized colloidal TiO2 films. Nature 353, 737–740 (1991).

  2. 2.

    Photoelectrochemical cells. Nature 414, 338–344 (2001).

  3. 3.

    , , & Dye-sensitized nanostructured p-type nickel oxide film as a photocathode for a solar cell. J. Phys. Chem. B 103, 8940–8943 (1999).

  4. 4.

    Limiting efficiencies of ideal single & multiple energy gap terrestrial solar cells. J. Appl. Phys. 51, 4494–4500 (1980).

  5. 5.

    et al. Sensitized hole injection of phosphorus porphyrin into NiO: Toward new photovoltaic devices. J. Phys. Chem. B 109, 22928–22934 (2005).

  6. 6.

    , , & Dye-sensitized nanostructured tandem cell-first demonstrated cell with a dye-sensitized photocathode. Sol. Energy Mater. Sol. Cells 62, 265–273 (2000).

  7. 7.

    & Fabrication and dye-sensitized solar cell performance of nanostructured NiO/Coumarin 343 photocathodes. Electrochem. Solid State Lett. 11, K78–K80 (2008).

  8. 8.

    , , & Photoinduced ultrafast dynamics of coumarin 343 sensitized p-type-nanostructured NiO films. J. Phys. Chem. B 109, 19403–19410 (2005).

  9. 9.

    et al. Improved photon-to-current conversion efficiency with a nanoporous p-type NiO electrode by the use of a sensitizer-acceptor dyad. J. Phys. Chem. C 112, 1721–1728 (2008).

  10. 10.

    et al. Charge-transfer processes in dye-sensitized NiO solar cells. J. Phys. Chem. C 112, 16134–16139 (2008).

  11. 11.

    et al. Design of an organic chromophore for p-type dye-sensitized solar cells. J. Am. Chem. Soc. 130, 8570–8572 (2008).

  12. 12.

    et al. Preparation and characterization of Eosin B- and Erythrosin J-sensitized nanostructured NiO thin film photocathodes. Thin Solid Films 490, 182–188 (2005).

  13. 13.

    , & Photoelectrochemistry of mesoporous NiO electrodes in iodide/triiodide electrolytes. J. Phys. Chem. C 111, 17455–17458 (2007).

  14. 14.

    , , , & Dye-sensitized nickel(II) oxide photocathodes for tandem solar cell applications. Nanotechnology 19, 295304–295313 (2008).

  15. 15.

    et al. A high voltage dye-sensitized solar cell using a nanoporous NiO photocathode. Chem. Lett. 34, 500–501 (2005).

  16. 16.

    et al. Cross surface ambipolar charge percolation in molecular triads on mesoscopic oxide films. J. Am. Chem. Soc. 127, 5706–5713 (2005).

  17. 17.

    Novel Head-to-Tail Coupled Oligo(3-Hexylthiophene) Derivatives for Photovoltaic Applications. PhD thesis, Univ. Ulm (2005).

  18. 18.

    et al. Design, synthesis, and application of amphiphilic ruthenium polypyridyl photosensitizers in solar cells based on nanocrystalline TiO2 films. Langmuir 18, 952–954 (2002).

  19. 19.

    , , & Tandem dye-sensitized solar cell for improved power conversion efficiencies. Appl. Phys. Lett. 84, 3397–3399 (2004).

  20. 20.

    , , , & Dye-sensitized solar cells: Improvement of spectral response by tandem structure. J. Photochem. Photobiol. A: Chem. 164, 33–39 (2004).

  21. 21.

    et al. Nanocrystalline dye-sensitized solar cell/copper indium gallium selenide thin-film tandem showing greater than 15% conversion efficiency. Appl. Phys. Lett. 88, 203103 (2006).

  22. 22.

    & Dye-sensitized solar cell using novel tandem cell structure. J. Phys. D 40, 1664–1668 (2007).

  23. 23.

    et al. Fabrication of thin film dye sensitised solar cells with a solar to electric power conversion efficiency over 10%. Thin Solid Films 516, 4613–4619 (2008).

Download references


The authors would like to thank the Victorian Government (Department of Primary Industries, ETIS SERD), the ARC Centre of Excellence for Electromaterials Science (ACES), the German Academic Exchange Service (DAAD-Go8 joint research cooperation scheme) and the International Science Linkage Project CG 100059 (DIISR, Australia) for financial support. Furthermore, they would like to acknowledge the ARC for providing equipment support through LIEF, as well as supporting U.B. with an Australian Research Fellowship. Special thanks also to Monash University for supporting U.B. with a Monash Research Fellowship, as well as JGC Catalysts and Chemicals Ltd, Kitakyushu-Shi (Japan) for providing samples of TiO2 screen-printing paste. We would like to thank the German Federal Ministry of Education and Research (BMBF) for financially supporting our research on organic solar-cell materials in the frame of a joint project (OPEG) and the Alexander von Humboldt Foundation for a grant for A.M. This work was also supported by the German Science Foundation (DFG) in the frame of a Collaborative Research Center (SFB 569). Finally we would also like to thank L. Kane-Maguire for assistance in the manuscript preparation process.

Author information

Author notes

    • P. Bäuerle
    •  & U. Bach

    These authors contributed equally to this work


  1. ARC Centre of Excellence for Electromaterials Science, Department of Materials Engineering, Monash University, Clayton Victoria, 3800, Australia

    • A. Nattestad
    • , Y.-B. Cheng
    •  & U. Bach
  2. ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, Innovation Campus, University of Wollongong, New South Wales, 2522, Australia

    • A. J. Mozer
  3. Institute for Organic Chemistry II and Advanced Materials, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany

    • M. K. R. Fischer
    • , A. Mishra
    •  & P. Bäuerle
  4. ARC Centre of Excellence for Electromaterials Science, School of Chemistry, Monash University, Clayton Victoria, 3800, Australia

    • U. Bach


  1. Search for A. Nattestad in:

  2. Search for A. J. Mozer in:

  3. Search for M. K. R. Fischer in:

  4. Search for Y.-B. Cheng in:

  5. Search for A. Mishra in:

  6. Search for P. Bäuerle in:

  7. Search for U. Bach in:


U.B. and P.B. proposed the research with further contributions from A.M. and Y.-B.C. A.N. carried out the photovoltaic characterization, optical analysis and optimized the tandem solar cells under the supervision of U.B. and Y.-B.C. Sensitizing dyes were designed and developed in the group of P.B. M.K.R.F. carried out the molecular orbital calculations. A.J.M. and U.B. executed the transient absorption spectroscopy measurements and interpreted the result. U.B., A.N., A.J.M. and M.K.R.F. were mainly responsible for writing the manuscript, with further inputs from P.B., Y.-B.C. and A.M.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to P. Bäuerle or U. Bach.

Supplementary information

PDF files

  1. 1.

    Supplementary Information

    Supplementary Information

About this article

Publication history






Further reading