Sodium Fluoride-Assisted Modulation of Anodized TiO<sub>2</sub> Nanotube for Dye-Sensitized Solar Cells Application Jung-Ho Yun Yun Hau Ng Changhui Ye Attila J. Mozer Gordon G. Wallace Rose Amal 10.1021/am200147b.s001 https://acs.figshare.com/articles/journal_contribution/Sodium_Fluoride_Assisted_Modulation_of_Anodized_TiO_sub_2_sub_Nanotube_for_Dye_Sensitized_Solar_Cells_Application/2648245 This work reports the use of sodium fluoride (in ethylene glycol electrolyte) as the replacement of hydrofluoric acid and ammonium fluoride to fabricate long and perpendicularly well-aligned TiO<sub>2</sub> nanotube (TNT) (up to 21 μm) using anodization. Anodizing duration, applied voltage and electrolyte composition influenced the geometry and surface morphologies of TNT. The growth mechanism of TNT is interpreted by analyzing the current transient profile and the total charge density generated during anodization. The system with low water content (2 wt %) yielded a membrane-like mesoporous TiO<sub>2</sub> film, whereas high anodizing voltage (70 V) resulted in the unstable film of TNT arrays. An optimized condition using 5 wt % water content and 60 V of anodizing voltage gave a stable array of nanotube with controllable length and pore diameter. Upon photoexcitation, TNTs synthesized under this condition exhibited a slower charge recombination rate as nanotube length increased. When made into <i>cis</i>-diisothiocyanato-bis(2,2̀-bipyridyl-4,4̀-dicarboxylato) ruthenium(II) bis (tetrabutyl-ammonium)(N719) dye-sensitized solar cells, good device efficiency at 3.33 % based on the optimized TNT arrays was achieved with longer electron time compared with most mesoporous TiO<sub>2</sub> films. 2011-05-25 00:00:00 60 V electrolyte composition surface morphologies anodizing voltage ethylene glycol electrolyte nanotube length device efficiency charge recombination rate electron time optimized TNT arrays pore diameter charge density growth mechanism TNT arrays sodium fluoride Anodized TiO 2 Nanotube mesoporous TiO 2 films Anodizing duration optimized condition 21 μ m ammonium fluoride hydrofluoric acid