Enhanced electron transport performance of TiO
2
nanorod arrays
electrode in dye-sensitized solar cells
Huayang Li, Hari Bala
n
, Guangyu Yuan, Xinglin Fu, Wuyou Fu
n
, Long Lin, Xiaodong Wang,
Jianliang Cao, Guang Sun, Zhanying Zhang
School of Materials Science and Engineering, Cultivating Base for Key Laboratory of Environment-Friendly Inorganic Materials in University of Henan
Province, Henan Polytechnic University, Jiaozuo 454000, People’s Republic of China
article info
Article history:
Received 18 June 2015
Received in revised form
7 August 2015
Accepted 12 August 2015
Available online 13 August 2015
Keywords:
TiO
2
nanorod arrays
Thin films
Solar energy materials
Solar cells
Electron transport
abstract
Oriented one-dimensional TiO
2
nanorod arrays (TNAs) thin film was grown on transparent conductive
glass substrate by hydrothermal method. After calcination, TNAs exhibited a vertically standing structure,
with average thickness of 1.21, 2.17
μ
m and diameter of 274, 333 nm, respectively. Then the as-prepared
TNAs were used as electrode to fabricated dye-sensitized solar cells (DSCs) with C106 sensitizer (Zhao
et al., 2013) [17], and the kinetic parameters of electron transport in TNAs-electrode were investigated.
Results showed that the TNAs-electrode DSCs exhibited longer electron lifetime and diffusion length
than that based on TiO
2
nanocrystals-electrode.
& 2015 Elsevier B.V. All rights reserved.
1. Introduction
As one of important wide gap oxide semiconductors, TiO
2
has
attracted considerable attention due to its low cost and chemical
stability [1]. It has been widely investigated in dye-sensitized solar
cell (DSCs) [2,3] and quantum dot-sensitized solar cells [4–6] in
recent years. Generally, TiO
2
nanocrystals thin film serves as both a
substrate for dye and the electron conductor in DSCs [7], which
provides not only the large surface area for dye absorption, but
also the pathway for electron transport. However, due to the re-
latively poor electron transport of TiO
2
nanocrystals, it is difficult
to further improve the photovoltaic properties of DSCs.
In order to improve the conversion efficiency of DSCs, synthe-
sizing one-dimensional TiO
2
nanostructure, including nanofibers
[8], nanotubes [9,10] and nanorods [11,12], has received great at-
tention due to their superior charge transport, such as efficient
separation and collection of all charge carriers, and low reflectance
[13]. However, there are few reports on the dynamic mechanisms
of DSCs based on one-dimensional TNAs. Therefore, a series of
micro processes including charge transport and recombination in
TNAs-electrode DSCs need to be systemically understood. In our
previous work, we found that the DSCs based on TiO
2
nanocrys-
tals/nanorods composites thin film had much lower
recombination rate and longer electron lifetime than that based on
TiO
2
nanocrystals [14]. In this work, we synthesized oriented one-
dimensional TiO
2
nanorod arrays (TNAs) on transparent con-
ductive glass substrate by hydrothermal method. The TNAs-elec-
trode DSCs were fabricated and the dynamic mechanism of elec-
tron transport was investigated.
2. Experimental
The preparation of TNAs on substrate was similar to that re-
ported in Ref. [11]. Typically, 10 mL of deionized water was mixed
with 10 mL of concentrated hydrochloric acid under stirring fol-
lowed by adding 0.3 mL titanium butoxide. After stirring for 5 min,
the above mixture was transferred into a Teflon-lined autoclave.
Then, one piece of FTO substrate that has been ultrasonically
cleaned in deionized water, acetone and ethanol was placed on the
bottom of Teflon liner vertically. After a hydrothermal reaction at
150 ° C for 290 min, the FTO substrate was rinsed with deionized
water and ethanol and dried in air to obtain Sample 01. The
Sample 02 was obtained by double treatment with the same hy-
drothermal procedure. The C106 [NaRu(4,4′-bis(5-(hexylthio)
thiophen-2-yl)-2,2′-bipyridine)(4-carboxylic acid-4′-carboxylate-
2,2′- bipyridine)(NCS)
2
] sensitizer was obtained from research
group of Prof. Wang (Chang Chun Institute of Applied Chemistry,
Chinese Academy of Sciences). The method for electrodes dye
sensitization and DSCs fabrication was same with our previous
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/matlet
Materials Letters
http://dx.doi.org/10.1016/j.matlet.2015.08.062
0167-577X/& 2015 Elsevier B.V. All rights reserved.
n
Corresponding authors.
E-mail addresses: hari@hpu.edu.cn (H. Bala), fuwy56@163.com (W. Fu).
Materials Letters 160 (2015) 572–575