TiO
2
nanocrystalline layer as a bridge linking TiO
2
sub-microspheres
layer and substrates for high-efficiency dye-sensitized solar cells
Yong Ding
a
, Li-E Mo
a
,LiTao
a
, Yan-Mei Ma
a
, Lin-Hua Hu
a
,
**
, Yang Huang
a
,
Xia-Qin Fang
a
, Jian-Xi Yao
b
, Xiao-Wang Xi
c
, Song-Yuan Dai
a
,
b
,
*
a
Key Laboratory of Novel Thin-Film Solar Cells, Division of Solar Energy Materials and Engineering, Institute of Plasma Physics,
Chinese Academy of Sciences, Hefei, Anhui 230031, PR China
b
State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206,
PR China
c
The College of Mechanical and Electrical Technology, Wuxi Institute of Technology, Wuxi, Jiangshu 214121, PR China
highlights
Effective photoelectrode is formed by monolayer nanocrystalline as a bridge.
The bridge can well solve the contact of TiO
2
sub-microspheres with FTO.
The bridge improves the charge collection efficiency.
The DSSC with this bridge achieves power conversion efficiency of 10.34%.
article info
Article history:
Received 24 May 2014
Received in revised form
31 July 2014
Accepted 2 September 2014
Available online 16 September 2014
Keywords:
Dye-sensitized solar cell
TiO
2
sub-microsphere
Electron transport
Electron recombination
abstract
TiO
2
sub-microspheres possess high surface area and superior light scattering effect which contributes to
the high photocurrent density (J
sc
) and power conversion efficiency (
h
) of dye-sensitized solar cells
(DSSCs). However, the poor interconnection between the TiO
2
sub-microspheres with substrates (N0S4)
restricts the electron transport and charge collection. In order to resolve this drawback, we adopted a
nanocrystalline monolayer as bridges to contact between the sub-microspheres and substrates (N1S3).
The improved contact provides more direct transport channels and increases the increased electron
concentration gradient from the top electrode to the bottom electrode, which accelerates the electron
transport and charge collection. The combined effects of the faster electron transport rate, less surface
states and higher collection effi ciency for the N1S3 based DSSC contribute to the higher J
sc
and
h
compared to the N0S4 based DSSC. While the photoelectrodes of N2S2 and N3S1 are too thick of
nanocrystalline layer to improve the performance of DSSCs due to the decreased dye loading, reduced
light scattering ability and increased crystal boundaries. As a result, a higher
h
of 10.34% is achieved by
introducing the nanocrystalline layer, whereas, only 9.17% is obtained for the photoelectrode without this
bridge.
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
Dye-sensitized solar cells (DSSCs), which emerged as a visible
light photovoltaic device, have been extensively investigated in
recent years due to their potential low production cost, high effi-
ciency and presenting attractive features [1,2]. In a DSSC, the per-
formance depends strongly on the dye adsorbed capacities, the
transfer of the photoinjected electrons through the network of TiO
2
photoelectrode and the dynamic processes of interfacial losses due
to the recombination with the I
3
[3]. TiO
2
photoelectrode, which is
considered as the backbone of DSSCs, commonly needs a large
* Corresponding author. Key Laboratory of Novel Thin-Film Solar Cells, Division of
Solar Energy Materials and Engineering, Institute of Plasma Physics, Chinese
Academy of Sciences, Hefei, Anhui 230031, PR China. Tel.: þ86 551 65593222.
** Corresponding author. State Key Laboratory of Alternate Electrical Power Sys-
tem with Renewable Energy Sources, North China Electric Power University, Beijing
102206, PR China. Tel.: þ86 10 61772268.
E-mail addresses: solarhu@sina.com, solar@ipp.ac.cn (L.-H. Hu), sydai@ipp.cas.
cn (S.-Y. Dai).
Contents lists available at ScienceDirect
Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
http://dx.doi.org/10.1016/j.jpowsour.2014.09.007
0378-7753/© 2014 Elsevier B.V. All rights reserved.
Journal of Power Sources 272 (2014) 1046e1052