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Bifacial dye-sensitized solar cells based on an ionic liquid electrolyte


Solar energy is a promising solution to global energy-related problems because it is clean, inexhaustible and readily available. However, the deployment of conventional photovoltaic cells based on silicon is still limited by cost, so alternative, more cost-effective approaches are sought. Here we report a bifacial dye-sensitized solar cell structure that provides high photo-energy conversion efficiency (6%) for incident light striking its front or rear surfaces. The design comprises a highly stable ruthenium dye (Z907Na) in combination with an ionic-liquid electrolyte and a porous TiO2 layer. The inclusion of a SiO2 layer between the electrodes to prevent generation of unwanted back current and optimization of the thickness of the TiO2 layer are responsible for the enhanced performance.

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Figure 1: Design of the bifacial DSC.
Figure 2: Relationship between the photovoltaic characteristics of bifacial DSCs with TiO2/SiO2 (3 µm thick) porous electrodes and the thickness of the porous TiO2 electrodes.
Figure 3: Experimental results of photovoltaic characteristics of DSCs with a porous TiO2 (16 µm thick) layer.
Figure 4: Electrical characteristics of the bifacial DSC.


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This work was supported by a grant from the Swiss Federal Energy Office (OFEN). The UV-curing glue and the SiO2 slurry (d = 600 nm) were provided by Three Bond (K. Kishi) and CCIC (T. Mizuno and T. Koyanagi), respectively.

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Authors and Affiliations



S.I. fabricated the TiO2 electrodes, TiO2/SiO2 electrodes and platinum electrodes, assembled cells, and performed the measurements for Figs 24. S.Z. synthesized the ruthenium dye (Z907) and the ionic liquid. P.C. synthesized the TiO2 nanoparticles. P.L. provided guidance on how to assemble the cells and equipment control. D.K. provided the details of the ionic–ionic liquid information. M.G. provided technical advice.

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Correspondence to Seigo Ito.

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Ito, S., Zakeeruddin, S., Comte, P. et al. Bifacial dye-sensitized solar cells based on an ionic liquid electrolyte. Nature Photon 2, 693–698 (2008).

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