Titanium dioxide coated zinc oxide nanostrawberry aggregates for
dye-sensitized solar cell and self-powered UV-photodetector
Caitian Gao
*
,
1
, Xiaodong Li
1
, Youqing Wang, Lulu Chen, Xiaojun Pan, Zhenxing Zhang,
Erqing Xie
*
School of Physical Science and Technology, Lanzhou University, Lanzhou, Gansu 730000, PR China
highlights graphical abstract
Preparation of ZnO nanostrawberry
aggregates with excellent light
scattering.
ZnO nanostrawberry aggregates film
induces large J
sc
and PCE in DSSCs.
Self-powered, ultrafast and visible
blind UV detection based on photo-
electrochemical cell.
article info
Article history:
Received 10 September 2012
Received in revised form
26 March 2013
Accepted 1 April 2013
Available online 8 April 2013
Keywords:
Zinc oxide nanostrawberry
Dye-sensitized solar cells
Self-powered
UV-photodetector
Light scattering
abstract
We report ZnO nanostrawberry aggregates (ZnO NS) structure that serves as photoanode for efficient
DSSCs as it offers a large specific surface area, excellent light scattering characteristics, and low degree of
charge recombination simultaneously. The short-circuit cu rrent density (J
sc
) of the ZnO NS DSSC is more
than two times higher than that of commercially-obtained ZnO nanocrystallines (ZnO NC) due to the
excellent light scattering of the ZnO NS film, resulting in a 46% improvement in the power conversion
efficiency (PCE). The introduction of TiO
2
coating layer on to the ZnO NS (ZnO NSeTiO
2
) results in more
than 82% enhancement in the PCE from 1.40% to 2.56%. Moreover, the photoelectrochemical cell (PECC)
with unsensitized ZnO NSeTiO
2
film as photoanode is applied to detect the UV light without a power
source. This self-powered UV-photodetector exhibits a high on/off ratio of 37,900, a fast rise time of
0.022 s and a decay time of 0.009 s for J
sc
signal, together with the excellent self-powered, “visible blind”
characteristics and photosensitivity linearity in a wide light intensity range.
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
Dye-sensitized solar cells (DSSCs) have been regarded as a
promising alternative to conventional solid-state semiconductor
solar cells due to their facile, low-cost, and environmental-friendly
fabrication process [1e3]. Nanostructured metal oxides are one of
key factors in determining the power conversion efficiency (PCE) in
DSSCs, because nanostructured networks provide a huge surface
area for dye loading and act as a media to transfer photogenerated
electrons to the transparent conductive oxide coated electrode. For
the DSSCs based on nanocrystalline TiO
2
films, competition be-
tween the generation and recombination of photogenerated car-
riers is a main bottleneck for further increase the PCE [4e6].
Various routes have been developed to solve this problem, such as
using one-dimensional nanostructures that are able to provide a
direct pathway for the rapid collection of photogenerated electrons
and, therefore, reduce the degree of charge recombination [3,7];
using the coreeshell structured photoanode to reduce the charge
recombination [3,5], and developing many novel three dimensional
photoanodes [8e11]. Unfortunately, these routes often lead to
*
Corresponding authors. Tel.: þ86 931 8912616; fax: þ86 931 8913554.
E-mail addresses: caitiangao10@163.com (C. Gao), xieeq@lzu.edu.cn (E. Xie).
1
These authors contributed equally to this work.
Contents lists available at SciVerse ScienceDirect
Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
0378-7753/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jpowsour.2013.04.003
Journal of Power Sources 239 (2013) 458e465