A Review of Chalcogenide Thin Films for Solar Cell Applications

Abstract

In this work, authors review the current state of research in chalcogenide thin films in order to study the use of films for the fabrication of cost-effective solar cells. As far as we know, various techniques have been employed to prepare thin films such as electro deposition, chemical bath deposition, flash evaporation, spray pyrolysis, successive ionic layer adsorption and reaction and so on. The obtained films showed that the band gap values are ranged from one to two eV which match to solar spectrum.

Full text

Abstract
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
*Author for correspondence
Indian Journal of Science and Technology, Vol 8(12), 67499, June 2015
ISSN (Print) : 0974-6846
ISSN (Online) : 0974-5645
A Review of Chalcogenide Thin Films for Solar Cell
Applications
Ho Soonmin1* and T. Joseph Sahaya Anand2
1Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Putra Nilai, 71800,
Negeri Sembilan, Malaysia; soonmin.ho@newinti.edu.my
2Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, 76109 Melaka, Malaysia
1. Introduction
e productions of various thin lms have been stud-
ied for many years. is is due to the properties of these
materials are suitable for application in solar cell, corro-
sion resistant coating, microelectronics, optics, magnetic,
laser devices and gas sensor devices. Currently, the most
used deposition methods to prepare these lms are
chemical bath deposition1–15, electro deposition16–23, ash
evaporation24–28, spray pyrolysis29–31, successive ionic layer
adsorption and reaction, magnetron sputtering35–37, Metal
organic chemical vapor deposition38,39. Keep in mind that
all these deposition methods have advantages and disad-
vantages depending on the type of application intended
for the lms.
Nowadays, much eort has been made by many
researchers to investigate the properties of thin lms
under various deposition conditions. Researchers work
hard to control the size, morphology and crystallinity of
the lms in order to produce high quality thin lms. In
this review paper, we have focused only on two favorable
properties which are used in solar cell such as band gap
and power conversion eciencies.
2. Results and Discussion
In last decades, the study of thin lms has increased
intensively because of the raw material can be obtained
easily, cheaper and abundant. Generally, there are vari-
ous thin lms are considered as potential candidates for
absorber materials of solar cells. It is because of band gap
energy range of 1.0 to 2.0 eV (Table 1), high absorption
coecient and successfully produce uniform layer so that
they can eciently absorb light on almost any surface.
At present, most of the authors have reported the prep-
aration and optimization of the thin lms by using various
physical and chemical deposition methods. Generally,
thin lms have been grown on the substrates from aque-
ous solutions. Following that, the obtained lms were
characterized using AFM, XRD, SEM, UV-Visible spec-
trophotometer, EDAX in terms of study the morphology,
composition, structure, optical and electrical conductiv-
ity. Authors claimed that they can produce good quality
Keywords:

A Review of Chalcogenide Thin Films for Solar Cell Applications
Indian Journal of Science and Technology
Vol 8 (12) | June 2015 | www.indjst.org
2
in lms Band gap Reference
SnSe 1.25 Zainal et al.40
SnS 1.0 Hankare et al.41
PbSe 1-1.3 Okereke and Ekpunobi42
PbS 1.8 Oriaku and Osuwa43
NiSe 1.61 Hankare et al.44
CoS 1.13 Mane et al.45
CdSe 1.8 Gopakumar et al.46
Cd Te 1.45 Laxman et al.47
Sb2S31.78 Nair et al.48
CdZnSe 1.7-2.3 Deo et al.49
PbMnS 1.5 Joshi et al.50
Ag-In-S 1.82 Lin et al.51
HgxCd1-xS1.76 Deshmukh et al.52
CdMnS 1.45-1.65 Oriaku et al.53
CuInSe21.04 Bari et al.54
Ag8SnS61.28-1.39 Yeh and Cheng55
Cu2ZnSnS41.5 Subramaniam et al.56
Cu2ZnSnS41.55 Shinde et al.57
Cu2ZnSnS41.6 Kumar et al.58
Ag2ZnSnS41.2 Yeh and Cheng55
Table 1. Band gap energy of various thin lms
of thin lms in the optimized experimental conditions
for the solar cell applications but unfortunately, did not
indicate the power conversion eciency to readers. In
other words, the power conversion eciencies should
be reported in their research ndings and their paper as
well before can be used in solar cells. Some examples are
shown below.
Song and Lee prepared ZnxCd1-xS lms using chemi-
cal bath deposition. e research ndings indicated that
the band gap and the pH of the solution decrease with
increasing concentration of zinc acetate. Cd0.5Zn0.5Se thin
lms were prepared by Kale et al. (2007) using chemi-
cal bath deposition method from aqueous solutions.
e band gap and electrical resistivity were 2.35 eV and
107Ωcm, respectively. e obtained lms consisted of
smaller and bigger particles because of the mixture of
cubic and hexagonal CdSe and ZnSe phases as shown in
XRD and AFM results.
e cadmium sulde thin lms grown at 80°C by
chemical bath deposition method and electro deposition
indicate poor crystallinity in XRD and SEM studies by
Ileperuma et al. In addition, these lms are n-type and
the band gap values are close to 2.4 eV. Fernandez and
Merino have reported for the rst time the preparation
of Sb-Se by electro deposition technique. ey have suc-
cessfully pointed out that the best conditions to produce

Ho Soonmin and T. Joseph Sahaya Anand
Indian Journal of Science and Technology 3
Vol 8 (12) | June 2015 | www.indjst.org
in lms %Method Reference
CdSe0.6Te 0.4 0.43 Chemical bath deposition Shinde et al.59
CdSe0.6Te 0.4 0.64 Electrodeposition Shinde et al.60
SnS 1.3 Spray pyrolysis Ramakrishna Reddy et al.61
CdIn2S42.94 electrodeposition Kokate et al.62
CdS 0.06 Chemical bath deposition Patil et al.63
Cd Te 0.136 Chemical bath deposition Patil et al.63
CdS0.5Te0.5 0.023 Chemical bath deposition Patil et al.63
MoBi2Se50.281 arrested precipitation technique Mane et al.64
ZnS0.5Se0.5 1.6 Close spaced evaporation Subbaiah et al.65
CuInSe23.1 Chemical bath deposition Vidyadharan Pillai and Vijayakumar66
SnS0.5Se0.5 Less than 1 electrodeposition Subramanian et al.67
CuInS22.4 Photoelectrochemical &
electrochemical anodic method Berenguier and Lewerenz68
Table 2. Power conversion ecacy for various thin lms
Sb2Se3 are using 0.04 M selenous acid and 0.1 M potas-
sium antimonyl tartrate with a potential of -0.8 V for
thirty ve mi of deposition.
A study of the growth of CuInS2 thin lms by using
electrodeposition method has been carried out by Asenjo
et al. (2006). XRD studies revealed that CuInS2 phase pre-
dominant for lms aer annealing at 200°C in nitrogen
atmosphere. However, X-ray photoelectron spectroscopy
indicated that the presence of CuInS2 in their samples
together with secondary phases such as In2S3, CuO/CuS
and Cu2O/Cu2S compositions.
Cathodic electrodeposition in the presence of ethyl-
enediaminetetraacetate as a chelating agent was used to
prepare Cu2S lms deposited on titanium substrate by
Anuar et al. (2002). e obtained results indicated that
the lms prepared are of p-type. Furthermore, the lms
prepared at -0.4 and -0.5 V have better photosensitivity.
Electrodeposited cadmium indium telluride lms have
direct band gap of 1.1 eV and indicate cubic phase in XRD
study by Kiran Jain (2003). According to SEM results, the
lms prepared at -0.54V show smooth and uniform sur-
faces with pinhole free appearance.
Todorov et al. (2006) have reported an atmospheric
pressure deposition technique for preparing CuInS2 lms.
e precursor lms are obtained by a solution coating
technique and then, are subjected to sulfurization treat-
ment in their experiments. e sulfurized lms are dense
and adhered to the substrate based on SEM studies.
ere are only a few reports of solar cell ecacy. Table
2 lists the original work that describe various thin lms
were prepared using dierent deposition methods for the
accuracy measurement of solar cell eciencies.
As shown in Table 2, the power conversion ecien-
cies for the various types of thin lms are below 7%. We
understand that the variable values are due to the several
reasons such as deposition methods, the nature of precur-
sors, growth conditions and deposition parameters. For
example, the lms grown at lower bath temperature may
provide good conversion eciencies if the post deposi-
tion treatment. Because of improve crystallinity of sample
aer surface treatment. In addition, these lms seem to
provide benet for the compactness of the absorber layer,
which would be preferentially for the smaller lm thick-
nesses by avoiding pin holes.

A Review of Chalcogenide Thin Films for Solar Cell Applications
Indian Journal of Science and Technology
Vol 8 (12) | June 2015 | www.indjst.org
4
3. Conclusion
is review article pointed out those thin lms could be
used as lows-cost solar cells. Currently, several binary,
ternary and quaternary thin lms are studied for their
potential for solar cell applications. e performance of
thin lms solar cells depend on the morphology, band
gap and structure of lms. In future works, more research
activities should focus to how to improve the power con-
version eciency in chalcogenide thin lms solar cells.
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