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Fabrication of nanoporous titania on glass and transparent conducting oxide substrates by anodization of titanium films

Published online by Cambridge University Press:  03 March 2011

Andrew J. Leenheer*
National Renewable Energy Laboratory, Golden, Colorado 80401
Alexander Miedaner
National Renewable Energy Laboratory, Golden, Colorado 80401
Calvin J. Curtis
National Renewable Energy Laboratory, Golden, Colorado 80401
Maikel F.A.M. van Hest
National Renewable Energy Laboratory, Golden, Colorado 80401
David S. Ginley
National Renewable Energy Laboratory, Golden, Colorado 80401
a) Address all correspondence to this author. e-mail:
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Nanoporous titania (TiO2) or titania nanotubes could provide a continuous nanostructured electron-conducting anode for organic photovoltaics. In this work, nanoporous titania was formed by anodizing thin films of titanium on both glass and transparent conducting oxide (TCO) substrates. Titanium thin films (500–700 nm) were deposited by radio frequency (RF) magnetron sputtering. Films were anodized in acidic electrolytes containing small amounts of hydrofluoric acid (HF) at constant voltages ranging from 7 to 15 V. Scanning electron microscope (SEM) analysis revealed a nanoporous structure. Nanoporous titania structures were grown on glass in an electrolyte containing sulfuric acid, trisodium citrate, and potassium fluoride, with pore diameters around 50 nm. Analyzing the films at different anodization times, the stages of nanopore formation were elucidated. Additionally, nanoporous titania was formed on a TCO substrate by anodizing in an electrolyte containing acetic acid and hydrofluoric acid. While not completely transparent, the nanoporous titania is promising for use in organic photovoltaics.

Copyright © Materials Research Society 2007

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