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Long vertically aligned titania nanotubes on transparent conducting oxide for highly efficient solar cells

Abstract

Dye-sensitized solar cells consist of a random network of titania nanoparticles that serve both as a high-surface-area support for dye molecules and as an electron-transporting medium. Despite achieving high power conversion efficiencies, their performance is limited by electron trapping in the nanoparticle film. Electron diffusion lengths can be increased by transporting charge through highly ordered nanostructures such as titania nanotube arrays. Although titania nanotube array films have been shown to enhance the efficiencies of both charge collection and light harvesting, it has not been possible to grow them on transparent conducting oxide glass with the lengths needed for high-efficiency device applications (tens of micrometres). Here, we report the fabrication of transparent titania nanotube array films on transparent conducting oxide glass with lengths between 0.3 and 33.0 µm using a novel electrochemistry approach. Dye-sensitized solar cells containing these arrays yielded a power conversion efficiency of 6.9%. The incident photon-to-current conversion efficiency ranged from 70 to 80% for wavelengths between 450 and 650 nm.

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Figure 1: Thick titanium films deposited on FTO-coated glass.
Figure 2: TNA films on FTO-coated glass.
Figure 3: Optical spectra of nanotube array films.
Figure 4: Performance of the DSCs fabricated using transparent nanotube array films.

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Acknowledgements

The authors acknowledge support for this work from the Department of Energy, grant no. DE-FG36-08GO18074.

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Authors

Contributions

M.P. conceived the idea, developed the anodization process and performed SEM imaging as well as DSC fabrication and characterization. O.K.V. conceived the idea and developed the process for coating titanium films, performed optical and structural studies as well as quantum efficiency measurements and composed the manuscript. M.P. and O.K.V. analysed the data. C.A.G. motivated and coordinated the work, supplied materials and analysis tools, and edited the manuscript.

Corresponding author

Correspondence to Craig A. Grimes.

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Varghese, O., Paulose, M. & Grimes, C. Long vertically aligned titania nanotubes on transparent conducting oxide for highly efficient solar cells. Nature Nanotech 4, 592–597 (2009). https://doi.org/10.1038/nnano.2009.226

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