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High-performance dye-sensitized solar cells based on solvent-free electrolytes produced from eutectic melts

Nature Materials volume 7, pages 626–630 (2008)Cite this article

Abstract

Low-cost excitonic solar cells based on organic optoelectronic materials are receiving an ever-increasing amount of attention as potential alternatives to traditional inorganic photovoltaic devices. In this rapidly developing field, the dye-sensitized solar cell1 (DSC) has achieved so far the highest validated efficiency of 11.1% (ref. 2) and remarkable stability3. However, the cells with the best performance use volatile solvents in their electrolytes, which may be prohibitive for outdoor solar panels in view of the need for robust encapsulation. Solvent-free room-temperature ionic liquids4,5,6,7,8,9,10,11 have been pursued as an attractive solution to this dilemma, and device efficiencies of over 7% were achieved by using some low-viscosity formulations containing 1-ethyl-3-methylimidazolium thiocyanate8, selenocyanate9, tricyanomethide10 or tetracyanoborate11. Unfortunately, apart from tetracyanoborate, all of these low-viscosity melts proved to be unstable under prolonged thermal stress and light soaking. Here, we introduce the concept of using eutectic melts to produce solvent-free liquid redox electrolytes. Using a ternary melt in conjunction with a nanocrystalline titania film and the amphiphilic heteroleptic ruthenium complex Z907Na (ref. 10) as a sensitizer, we reach excellent stability and an unprecedented efficiency of 8.2% under air-mass 1.5 global illumination. Our results are of importance to realize large-scale outdoor applications of mesoscopic DSCs.

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Figure 1: Plots of specific conductivity (σ) of imidazolium melts versus temperature (T).
Figure 2: Stokes–Einstein plots of diffusion coefficient (D) versus fluidity (η−1).
Figure 3: Photocurrent density–voltage (J–V) characteristics of devices A and B under AM 1.5G illumination (100 mW cm−2).
Figure 4: Detailed photovoltaic parameters of a cell measured under the irradiance of AM 1.5G sunlight during successive full-sun visible-light soaking at 60 ∘C.
Figure 5

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Acknowledgements

The National Key Scientific Program-Nanoscience and Nanotechnology (No. 2007CB936700), the National Science Foundation of China (50773078) and the ‘100-Talent Program’ of the Chinese Academy of Sciences have supported this work. M.W., S.M.Z. and M.G. thank G. Rothenberger for helpful discussions and the Swiss National Science Foundation for financial support. P.W. thanks EPFL for a visiting professorship.

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  1. Yu Bai and Yiming Cao: These authors contributed equally to this work

Authors and Affiliations

  1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China

    Yu Bai, Yiming Cao, Jing Zhang, Renzhi Li & Peng Wang

  2. Laboratory for Photonics and Interfaces, Swiss Federal Institute of Technology, CH 1015, Lausanne, Switzerland

    Mingkui Wang, Shaik M. Zakeeruddin & Michael Grätzel

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  1. Yu Bai
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Correspondence to Peng Wang or Michael Grätzel.

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Bai, Y., Cao, Y., Zhang, J. et al. High-performance dye-sensitized solar cells based on solvent-free electrolytes produced from eutectic melts. Nature Mater 7, 626–630 (2008). https://doi.org/10.1038/nmat2224

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