(321h) 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 /cm²of 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.