Effect of boron-doping on the luminescent and electrical properties of a
CdS/Si heterostructure based on Si nanoporous pillar array
Ling Ling Yan
a,b
, Xiao Bo Wang
a,c
, Xiao Jun Cai
a
, Xin Jian Li
a,
⇑
a
Department of Physics and Laboratory of Material Physics, Zhengzhou University, Zhengzhou 450052, People’s Republic of China
b
College of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000, People’s Republic of China
c
College of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000, People’s Republic of China
article info
Article history:
Received 17 October 2014
Received in revised form 21 January 2015
Accepted 22 January 2015
Available online 3 February 2015
Keywords:
Silicon nanoporous pillar array (Si-NPA)
Cadmium sulfide (CdS)
Boron-doping
Photoluminescence
Electrical rectification effect
abstract
Using silicon nanoporous pillar array (Si-NPA) as substrates and boric acid as dopant source, a series of
CdS/Si nanoheterostructures were prepared by growing B-doped CdS thin films on Si-NPA via a chemical
bath deposition (CBD) method. The structural, optical and electrical properties of CdS/Si-NPA were
studied as a function of the [B]/[Cd] ratio of the initial CBD solutions. Our results disclosed that B concen-
tration could be tuned effectively through changing the ratio of [B]/[Cd], which would bring large
variation on the optical and electrical properties of CdS/Si-NPA without affecting its crystal structure
and surface morphology. The samples with optimal optical and electrical properties were prepared with
[B]/[Cd] = 0.01, in which the physical properties of relatively strong light absorption, small electrical
resistivity, low turn-on voltage, small leakage current density and high breakdown voltage could be
obtained. These results indicated that B-doping might be an effective path for promoting the performance
of the optoelectronic devices based on CdS/Si-NPA.
Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction
In the past decades, cadmium sulfide (CdS) nanostructures have
been studied intensively due to their potential applications in fab-
ricating photovoltaic cells [1,2], light-emitting diodes [3], laser
diodes [4], and waveguide devices [5]. In the studies, different
preparing techniques, such as spray pyrolysis [6], close-spaced
sublimation [7], chemical vapor deposition [8] and chemical bath
deposition (CBD) [7], have been adopted to grow CdS films on
various functional substrates. Among the techniques, CBD method
is proved to be an effective one for preparing high-quality CdS
thin films with large-area uniformity, strong adhesive force and
high preparation reproducibility. Silicon nanoporous pillar array
(Si-NPA) is a silicon hierarchical structure characterized by its
unique regular array consisted of micron-sized, quasi-identical
and nanoporous silicon pillars and featured by its high light-
absorption across the ultraviolet–visible-infrared region and
strong visible photoluminescence (PL) at room temperature [9].
These morphological and physical properties indicated that
Si-NPA might be an ideal candidate both as a functional silicon
nanostructure itself and a template for assembling silicon-based
optoelectronic nanosystems in constructing nanodevices such as
solar cells [1], light-emitting diodes [10], electrical rectifying
devices [11] and nanosensors [12].
In the previous study, we reported that a CdS/Si nanohetero-
structure was prepared through growing CdS thin film on Si-NPA
by a CBD method, in which obvious rectification behavior and
photovoltaic effect were observed [1,11]. This indicated that
CdS/Si-NPA might be a promising candidate for assembling high-
efficiency novel solar cells. Nevertheless, the device exhibited a
small short circuit current and a big series resistance (R
s
), which
led to a relatively low energy conversion efficiency [1]. Through
analyzing the influence of the technical parameters on the device
performance, the relatively big R
s
was thought to be the dominant
reason. It has been proved both theoretically and experimentally
that a big R
s
for a cell would bring obvious reduction of its fill factor
and short circuit current, and therefore lead to the lowering of its
energy conversion efficiency [13,14]. According to the device struc-
ture of a solar cell, the origin of R
s
should include the resistance
arose from the semiconductor materials, the metallic contacts at
the electrodes, and the massive interconnects within the nano-
structures. Combined with the analysis on the electrical conductiv-
ity of CdS thin film [15], the R
s
should mainly come from the high
resistance of as-deposited CdS film, which is difficult to be further
lowered just by controlling preparation conditions in the CBD
process. To solve the problem, a commonly used method is to
introduce suitable exotic atoms, such as by doping CdS thin film
http://dx.doi.org/10.1016/j.jallcom.2015.01.177
0925-8388/Ó 2015 Elsevier B.V. All rights reserved.
⇑
Corresponding author. Tel./fax: +86 371 67766629.
E-mail address: lixj@zzu.edu.cn (X.J. Li).
Journal of Alloys and Compounds 632 (2015) 450–455
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jalcom