Dye-sensitization of self-assembled titania nanotubes prepared by galvanostatic anodization of Ti sputtered on conductive glass

Abstract

Self-organized porous TiO(2) nanotubes (NTs) were prepared on conductive glass by galvanostatic anodizing of sputtered titanium in an NH(4)F /glycerol electrolyte. DC magnetron sputtering at an elevated substrate temperature (500 degrees C) was used to deposit 650 nm thick titanium films. After anodizing, NTs, 830 nm long, with an average external diameter of 92 nm, were grown; this gave a high conversion rate of oxide from titanium (1.9), with a 220 nm thick layer of titanium, which was not oxidized, located at the base of the tubes. The NTs revealed a mainly amorphous structure, which transformed mostly to anatase upon thermal treatment in air at 450 degrees C. The tubes were sensitized by the N719 complex and the resultant photoelectrodes were incorporated into liquid dye solar cells (DSCs) and further tested under back-side illumination. High values of V(oc) (714 mV) were obtained under 1 sun (AM 1.5), assigned to low dark current magnitude and large recombination resistance and electron lifetime. In addition, typical values of fill factors (of the order of 0.62) were attained, in agreement with the estimated ohmic resistance of the cells in combination with low electron transfer resistance at the platinum/electrolyte interface. The overall moderate power conversion efficiency (of the order of 0.3%) was mainly due to the low short-circuit photocurrents (J(sc) = 0.68 mA cm(-2)), which was confirmed further by the corresponding IPCE values (5.2% at 510 nm). The magnitude of J(sc) was attributed to absorbed light losses due to back-side illumination of the cells, the low dye loading (due to the limited thickness of anodic titania) and the high charge transfer resistance at the TiO(2)/conductive substrate due to the presence of barrier layer(s) underneath the tubes. These preliminary results encourage the DSC community to explore further the galvanostatic anodizing of titanium in order to produce highly efficient porous TiO(2) NTs directly on conductive glass. Current work is focusing on achieving complete anodizing of the metal substrate and full transparency for the photoelectrode in order to increase and optimize the resultant cell efficiencies.

TiO2 nanotube formation by Ti film anodization and their transport properties for dye-sensitized solar cells

“…Furthermore, recombination resistant, R ct , was obtained 55.03 X that is comparable with literature data [26], implying that recombination of electrons through the electrolyte is not the dominant effect limiting photovoltaic performance.…”

PEG-Coated Titania Nanatubes for Controlled Drug Release

“…Song et al [5] found that 90% of horseradish peroxidase was released in the first minute from untreated TiO 2 nanotubes and adding hydrophobic monolayer of octadecylphosphonic acid only improved the release rate by less than two orders. TNTs have been fabricated on a range of non-native substrates including silicon, glass, transparent conducting oxide (TCO)-coated glass, polyimide, and stainless steel [7][8][9][10][11][12][13] .Highly ordered titania nanotube (TNT) arrays on Ti surface fabricated by self-ordering electrochemical anodization have attracted increasing attention due to their excellent biocompatibility, high surface-to-volume ratio,…”

Morphological studies of vertical arrays TiO2 nanotubes by electrochemical anodization technique for dye sensitized solar cell application

“…A few attempted to prepare TiO 2 nanotubes array directly on a transparent conductive substrate as a way to overcome the back-side illumination effects [3,[23][24]. The fabrication of this structured photoelectrode requires a deposition of metal titanium film on the conductive glass substrate in advance and causing the titanium film to undergo an anodization, resulting in the formation of nanotubes structure.…”