Hindawi Publishing Corporation International Journal of Photoenergy Volume 2013, Article ID 280253, 8 pages http://dx.doi.org/10.1155/2013/280253 Research Article Dye-Sensitized Solar Cells with Anatase TiO 2 Nanorods Prepared by Hydrothermal Method Ming-Jer Jeng, 1 Yi-Lun Wung, 1 Liann-Be Chang, 1 and Lee Chow 2 1 Department of Electronic Engineering and Green Technology Research Center, Chang-Gung University, Taoyuan 333, Taiwan 2 Department of Physics, University of Central Florida, Orlando, FL 32816, USA Correspondence should be addressed to Ming-Jer Jeng; mjjeng@mail.cgu.edu.tw Received 29 June 2013; Revised 20 August 2013; Accepted 6 September 2013 Academic Editor: Stefano Caramori Copyright © 2013 Ming-Jer Jeng et al. his 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. he hydrothermal method provides an efective reaction environment for the synthesis of nanocrystalline materials with high purity and well-controlled crystallinity. In this work, we started with various sizes of commercial TiO 2 powders and used the hydrothermal method to prepare TiO 2 thin ilms. We found that the synthesized TiO 2 nanorods were thin and long when smaller TiO 2 particles were used, while larger TiO 2 particles produced thicker and shorter nanorods. We also found that TiO 2 ilms prepared by TiO 2 nanorods exhibited larger surface roughness than those prepared by the commercial TiO 2 particles. It was found that a pure anatase phase of TiO 2 nanorods can be obtained from the hydrothermal method. he dye-sensitized solar cells fabricated with TiO 2 nanorods exhibited a higher solar eiciency than those fabricated with commercial TiO 2 nanoparticles directly. Further, triple-layer structures of TiO 2 thin ilms with diferent particle sizes were investigated to improve the solar eiciency. 1. Introduction Dye-sensitized solar cells (DSSCs) have attracted much atten- tion as possible candidates for low cost, high stability, and high eicient solar cells [1, 2]. here are many innovations in this emerging technology such as new dyes which are absorbed at a wider range of wavelengths and the intro- duction of nanostructure titanium oxides (TiO 2 ) to increase the surface area [3–5]. he DSSCs with the nanostructure titanium oxide/Porphyrins dye thin ilms on transparent conducting oxide- (TCO-) coated glass can achieve a solar eiciency as high as 13% [6]. he major improvements of the research are made not only by introducing highly absorbing dyes as light harvesters, but also by using the nanostructure layer to improve the absorption and collection eiciency. In principle, fast electron transport and slow recombination will be needed to obtain a high solar conversion eiciency. For conventional DSSC, the mesoporous ilm consisted of nanocrystalline TiO 2 particles, enjoying the advantages of a large surface for greater dye adsorption and facilitating electrolyte difusion within their pores [7–12]. he hydrother- mal method provides an efective reaction environment for the synthesis of nanocrystalline TiO 2 with high purity and well-controlled crystallinity [13–15]. herefore, we use the hydrothermal method to prepare TiO 2 thin ilms in this work. he Taguchi method [16–20] is used to ind the optimal parameters for the formation of high-quality TiO 2 ilms. he Taguchi method [16] is a process optimization technique that investigates how multiparameters afect the performance of a process. It can minimize the variation in a process through robust design of experiments. he Taguchi method uses orthogonal arrays [17] to organize the parameters afecting the process and the levels at which they should be varied. It allows for the determination of factors mostly afecting a process performance characteristic with a minimum amount of experimentation. Generally, it employs a generic signal- to-noise (/) ratio to quantify the variation. hese / ratios are used as measures of the efect of noise factors on performance characteristics. here are several / ratio types of characteristics: larger is better, nominal is best, smaller is better, and so forth [16, 18]. In addition, it is known that the strong back-scattering light due to the large particles near the conducting glass results in a light loss. To reduce light loss due to this strong back-scattering light, multiple-layer structure of TiO 2 with