Synthesis of High Aspect-Ratio ZnO Nanowires By CVD Method

Synthesis of High Aspect-Ratio ZnO Nanowires by CVD Method

 

 

Yang Zhao^1,*, Cheng Xu^1,2, Jie Liu¹, Yongjie Zou², and Kirk J. Ziegler^1,2

 

¹ Department of Chemical Engineering

² Department of Materials Science and Engineering

 

University of Florida, Gainesville, FL 32611*Presenting Author (Ph: 352-392-3122; Email: yangzhao@ufl.edu)

 

Abstract: 

Dye-sensitized solar cells (DSSCs) have been extensively studied for the past few years because of their low-cost and high-efficiency. The surface area of the photoanode, which determines the amount of photons absorbed, is one of the most critical factors to improve the efficiency of DSSCs. Although conventional TiO₂ nanoparticle-based DSSCs have shown promising results, their performance has been limited to ~11% because of diffusion and back reaction problems.  Due to its excellent band gap (3.37eV) and high excitation bonding energy (60 meV) properties, one-dimensional (1D) ZnO nanowires are capable of overcoming the limitation of nanoparticle-based DSSCs by improving electron injection and axial electron diffusion. Based on models proposed by our group, the efficiency of DSSCs based on TiO₂ core-shell ZnO nanowires (40 µm in lengths, 40 nm in diameter and ~10¹¹ /cm² of density) can significantly surpass current efficiencies. To reach our objective, we focused on using two-step anodized aluminum oxide (AAO) as a template to control the dimension of nanowires. The synthesis of ZnO nanowires was carried out using thermal decomposition of zinc acetate dehydrate in the AAO pores by low temperature, catalyst-free vapor-solid (VS) growth. After transferring embedded ZnO nanowires to a PDMS substrate, AAO was etched and an electrostatic repulsion technique was applied to provide vertically-aligned ZnO nanowires. After that, SEM, TEM, and XRD were applied to characterize these nanowires. By using this technique, it provides a new approach to obtain vertically-aligned ZnO nanowires with both high density and aspect-ratio through a large-scale process.

Keywords: Dye sensitized solar cell (DSSC), ZnO Nanowires, Alumina Template, Thermal Decomposition.