Browsing by Author "Kuo, Yu-Yen"

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Hydrothermal crystallization and modification of surface hydroxyl groups of anodized TiO2 nanotube-arrays for more efficient photoenergy conversion
(2012-09-01)
Kuo, Yu-Yen
;
Li, Tze-Huei
;
Yao, Jing-Neng
;
Lin, Chiung-Yuan
;
Chien, Chao-Hsin
This paper describes a crystallization method for anodized TiO2 nanotube-array using a hydrothermal process. Pre-sintered TiO2 nanotube-array could further crystallize without experiencing a collapse of the nanotubes under the hydrothermal environment. Applying the hydrothermal crystallization method, the transition of surface bonds of nanotube from Ti-O to Ti-OH/Ti-OH2 can be controlled by acidic hydrothermal pH levels. Dissolution and structural transformation of nanotubes was easily induced if the hydrothermal environment became basic. These effects depicted great influence on the anchoring of carboxylate groups on the surface of TiO2 nanotubes and affected the performance of the dye-sensitized solar cell utilizing the hydrothermally crystallized TiO2 nanotubes as the photoelectrode. The photoenergy conversion efficiency increased from 6.40% for thermally annealed nanotubes to 7.13% for hydrothermally crystallized ones under illumination of 100 rnW cm(-2). (C) 2012 Elsevier Ltd. All rights reserved.
Sinter-free transferring of anodized TiO2 nanotube-array onto a flexible and transparent sheet for dye-sensitized solar cells
(2013-02-28)
Kuo, Yu-Yen
;
Chien, Chao-Hsin
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A sinter-free method to transfer anodized TiO2 nanotube-arrays to a polyethylene terephthalate (PET) sheet is proposed. Since the anodized nanotube-array was crystallized independently before transferring to the PET, the internal charge transport resistance and the charge recombination rate are unchanged for the nanotubes on the PET sheet, and no high temperature sintering process is required. With hydrothermal treatment, the dye sensitized solar cell fabricated utilizing a low temperature bonded nanotube/PET as a photoelectrode exhibits a power conversion efficiency of 5.41%, which is only 0.87% lower than the power conversion efficiency of the solar cell using nanotubes bonded on a conductive glass through high temperature processes. (C) 2013 Elsevier Ltd. All rights reserved.