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Nanostructured Zinc Stannate as Semiconductor Working Electrodes for Dye-Sensitized Solar Cells

Teresa Lana-Villarreal,* Gerrit Boschloo, and Anders Hagfeldt

Center of Molecular Devices, Department of Chemistry, Royal Institute of Technology, Teknikringen 30, SE-10044 Stockholm, Sweden

J. Phys. Chem. C, 2007, 111 (14), pp 5549–5556

DOI: 10.1021/jp0678756

Publication Date (Web): March 22, 2007

To whom correspondence should be addressed. E-mail: Teresa.Lana@ua.es.

Abstract

Zinc stannate (Zn₂SnO₄) particles with 27-nm size were synthesized by hydrothermal treatment. Nanoporous Zn₂SnO₄ thin films were prepared on conducting glass substrates and used as working electrodes in dye-sensitized solar cells, DSSC. Their behavior was compared with standard TiO₂ cells, using (TBA)₂-cis-Ru(Hdcbpy)₂(NCS)₂ (known as N719) as a dye and an electrolyte containing 0.7 M LiI and 0.05 M I₂ in 3-methoxypropionitrile. Under the same working conditions, Zn₂SnO₄ DSSC showed higher open-circuit potential, but their overall efficiency was lower due to their lower incident photon-to-current conversion efficiency. The properties of electrons in DSSC have been studied by measuring their transport time and lifetime by photocurrent and photovoltage transient measurements, respectively. The electron diffusion length is similar in both oxides, demonstrating the possible use of Zn₂SnO₄ as an electron collector in DSSC applications. On the other hand, photoinduced absorption measurements reveal problems in the electron injection from the dye to Zn₂SnO₄, owing to the higher position of its conduction band, in agreement with the higher open-circuit potential measured. Zinc stannate will be an interesting mesoporous material for DSSC, provided the use of dyes with a higher position of the LUMO compared to that of N719, as it will permit attaining higher photovoltages without affecting the photocurrent.