Highly efficient water splitting by a dual-absorber tandem cell


Photoelectrochemical water-splitting devices, which use solar energy to convert water into hydrogen and oxygen, have been investigated for decades. Multijunction designs are most efficient, as they can absorb enough solar energy and provide sufficient free energy for water cleavage. However, a balance exists between device complexity, cost and efficiency. Water splitters fabricated using triple-junction amorphous silicon1,2 or IIIV3 semiconductors have demonstrated reasonable efficiencies, but at high cost and high device complexity. Simpler approaches using oxide-based semiconductors in a dual-absorber tandem approach4,5 have reported solar-to-hydrogen (STH) conversion efficiencies only up to 0.3% (ref. 4). Here, we present a device based on an oxide photoanode and a dye-sensitized solar cell, which performs unassisted water splitting with an efficiency of up to 3.1% STH. The design relies on carefully selected redox mediators for the dye-sensitized solar cell6,7 and surface passivation techniques8 and catalysts9 for the oxide-based photoanodes.

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Figure 1: General schemes and energy diagrams for a photoanode/DSC D4 tandem cell.
Figure 2: Spectral response and J–V characteristics.
Figure 3: Faradaic efficiency measurement of a tandem cell.


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J.B. and T.H. acknowledge funding from the Swiss Federal Office of Energy (PecHouse2, SI/50090-02). J-H.Y. acknowledges support from the Korea Foundation for International Cooperation in Science and Technology through the Global Research Lab. M.C. acknowledges Toyota Motor Corp. for financial support. The authors thank P. Comte and F. Kessler for assistance in preparing the TiO2 paste and the cobalt complex. The authors also thank NEC corporation (Japan) for providing the Y123 dye.

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J.B., M.G. and K.S. conceived the experiment. K.S. directed the experimental work and J.B. performed the experiments. J-H.Y. prepared the DSC. M.C. prepared the haematite photoanodes. R.S. and J.A. prepared the WO3 photoanodes. T.H. measured the Faradaic efficiency. J.B. and K.S. wrote the manuscript.

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Correspondence to Kevin Sivula.

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Brillet, J., Yum, J., Cornuz, M. et al. Highly efficient water splitting by a dual-absorber tandem cell. Nature Photon 6, 824–828 (2012). https://doi.org/10.1038/nphoton.2012.265

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