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International Journal of Photoenergy
Volume 2012, Article ID 401393, 6 pages
Research Article

Alumina and Hafnia ALD Layers for a Niobium-Doped Titanium Oxide Photoanode

1Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
2Physics Department, Al-Azhar University-Gaza, P.O. Box 1277, Gaza, Palestine

Received 13 November 2012; Accepted 18 December 2012

Academic Editor: Sudhakar Shet

Copyright © 2012 Naji Al Dahoudi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Niobium-doped titanium dioxide (TiO2) nanoparticles were used as a photoanode in dye-sensitized solar cells (DSCs). They showed a high photocurrent density due to their higher conductivity; however, a low open-circuit voltage was exhibited due to the back-reaction of photogenerated electrons. Atomic layer deposition is a useful technique to form a conformal ultrathin layer of Al2O3 and HfO, which act as an energy barrier to suppress the back electrons from reaching the redox medium. This resulted in an increase of the open-circuit voltage and therefore led to higher performance. HfO showed an improvement of the light-to-current conversion efficiency by 74%, higher than the 21% enhancement obtained by utilizing Al2O3 layers.