XRD, SEM and photoelectrochemical characterization of ZnSe electrodeposited on Cu and Cu-Sn substrates

Article abstract of DOI:10.1016/j.electacta.2012.03.103

XRD, SEM and photoelectrochemical examinations of deposits formed on the Cu substrate by electrochemical deposition in a water solution containing 0.2 mol dm^-3 of ZnSO₄ and 0.002 mol dm^-3 of H ₂SeO₃ were performed. Formation of Cu₂Se _x at potentials positive to that of electrochemical deposition of ZnSe was proved by the XRD technique. The formation of Cu₂Se _x continued even after deposition due to further diffusion of the deposited Se into Cu. A nano-crystalline ZnSe of cubic structure was electrodeposited at a potential of -0.62 V vs. Ag/AgCl electrode and XRD examination of deposits formed using cyclic potential scanning and pulse plating revealed the presence of hexagonal ZnSe along with the cubic one. A photoelectrochemical characterization proved that the electrodeposited ZnSe was a p-type semiconductor. A significant amount of Cu₂Se_x was formed during annealing of ZnSe electrodeposited on the Cu substrate although only traces of copper selenide were detected before the annealing. ZnSe, SnSe and a small quantity of Cu₂Se_x were detected by XRD after annealing of ZnSe electrodeposited on the Cu-Sn/Mo/glass substrate.

Full text of DOI:10.1016/j.electacta.2012.03.103

Electrochimica Acta 70 (2012) 118–123
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Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
XRD, SEM and photoelectrochemical characterization of ZnSe electrodeposited
on Cu and Cu–Sn substrates
Remigijus Jusˇke˙ nas∗,1, Darius Avizˇinis, Putinas Kalinauskas, Algirdas Selskis1, Raimondas Giraitis,
Vidas Paksˇtas, Violeta Karpavicˇiene˙ , Stase˙ Kanapeckaite˙ , Zenius Mockus, Rokas Kondrotas
State Research Institute Center for Physical Sciences and Technology, Institute of Chemistry, A. Gosˇtauto 9, LT-01108 Vilnius, Lithuania
a r t i c l e i n f o
a b s t r a c t
Article history:
XRD, SEM and photoelectrochemical examinations of deposits formed on the Cu substrate by electro-
chemical deposition in a water solution containing 0.2 mol dm−3 of ZnSO4 and 0.002 mol dm−3 of H2SeO3
were performed. Formation of Cu2Sex at potentials positive to that of electrochemical deposition of ZnSe
was proved by the XRD technique. The formation of Cu2Sex continued even after deposition due to further
diffusion of the deposited Se into Cu. A nano-crystalline ZnSe of cubic structure was electrodeposited at a
potential of −0.62 V vs. Ag/AgCl electrode and XRD examination of deposits formed using cyclic potential
scanning and pulse plating revealed the presence of hexagonal ZnSe along with the cubic one. A pho-
toelectrochemical characterization proved that the electrodeposited ZnSe was a p-type semiconductor.
A significant amount of Cu2Sex was formed during annealing of ZnSe electrodeposited on the Cu sub-
strate although only traces of copper selenide were detected before the annealing. ZnSe, SnSe and a small
quantity of Cu2Sex were detected by XRD after annealing of ZnSe electrodeposited on the Cu–Sn/Mo/glass
substrate.
Received 2 December 2011
Received in revised form 10 March 2012
Accepted 10 March 2012
Available online 27 March 2012
Keywords:
Electrodeposition
Zinc selenide
Photoelectrochemical response
XRD
© 2012 Elsevier Ltd. All rights reserved.
1. Introduction
strates such as Ti [5–10,12], glass coated with ITO (indium doped
tin oxide) or FTO (fluorine doped tin oxide) [5–9,11,17], stainless
ZnSe is an n-type semiconductor with a wide band gap (2.7 eV)
and has a lot of technological applications. The electrodeposition of
ZnSe has been intensively investigated during past 30 years. One of
the most promising appliances of the electrodeposited ZnSe could
be fabrication of the CZTSe (Cu2ZnSnSe4) absorber layer for thin
film solar cells [1,2]. Instead of electrodeposition of stacked layers
of Cu, Sn and Zn, ZnSe could be deposited on a Cu–Sn layer. The elec-
trodeposition of ZnSe instead of Zn can make it possible to avoid an
insertion of Zn(OH)2/ZnO into the deposit which usually takes place
when cyanide-free solutions are used for the electrodeposition of
Zn or Zn alloys [3,4].
steel (SS) [11,12], Au [5,15], Cu [13,14]. The electrodeposited ZnSe
is predominantly reported to have a cubic structure except when
it was electrodeposited on the SS or Al substrates on which ZnSe
possessed a hexagonal structure [12]. It has been reported that
electrodeposited zinc selenide was a p-type semiconductor [5].
The electrodeposition of ZnSe on the Cu substrate was compre-
hensively studied by Kowalik et al. [13,14]. The electrolyte solution
containing 0.2 mol dm−3 ZnSO4 and 0.002 mol dm−3 H2SeO3 was
determined as the most suitable one for electrodeposition of ZnSe,
the most preferable potential and solution temperature ranges
were also established [13].
The electrodeposition of ZnSe has been investigated mainly in
water solutions [5–16] though in organic ones it has also been
reported [17]. In general zinc sulphate aqueous solutions to which a
small quantity of Se is added in the form of H2SeO3 or SeO2 are used
[5–10,12,13]. Different solutions such as acetate [13], perchlorate
[15], and solutions containing zinc EDTA (ethylene diamine tetrac-
etate) complex and selenium sulphite [8] have been examined.
The electrodeposition of ZnSe was carried out on different sub-
When considering a possibility to use the electrodeposition of
ZnSe for the electrochemical approach of the CZTSe fabrication it
could be useful to conduct more detailed studies of ZnSe deposition
on the copper substrate as one of the possible routes of the elec-
trochemical formation of copper selenide can proceed through the
reaction proposed by Kazacos and Miller [16]:
2Cu + H2SeO3 + 4e− + 4H+ → Cu2Se + 3H2O
(1)
However, as yet it has not been evidenced by XRD the Cu2Se
is formed during the electrochemical ZnSe deposition on the Cu
substrate. It has been reported that only amorphous selenium was
detected on the Cu substrate when the electrochemical deposition
was carried out in the potential range from 0 to −0.5 V vs. SCE
∗
Corresponding author. Tel.: +370 5 264 8881; fax: +370 5 264 9774.
E-mail address: juskenas@ktl.mii.lt (R. Jusˇke˙ nas).
ISE member.
1
0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.electacta.2012.03.103

R. Jusˇke˙ nas et al. / Electrochimica Acta 70 (2012) 118–123
119
[13,14]. Even after 2 h of heat treatment of the electrodeposited
0.5
0.0
-0.31 V
A2
-0.40 V
A1
ZnSe on Cu in Ar atmosphere at 300 ◦C formation of copper selenide
was not detected by XRD [13]. Nevertheless, on the basis of the
data obtained using voltammetry combined with the quartz crystal
microbalance technique the assumption was made that the elec-
trodeposited Se interacts with Cu at least during the first cycle of
electrodeposition [14].
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
E / V
-0.5
-1.0
-1.5
-2.0
C2
-0.48 V
C1
-0.08 V
In this work we present electrochemical, XRD, SEM along with
EDX and photoelectrochemical investigations of electrodeposits
formed on the Cu substrate in aqueous zinc sulphate solutions with
selenious acid. We used a combined electrochemical striping/XRD
approach [4,18] while attempting to get more information about
the crystalline phases formed. We also applied heat treatment of
electrodeposited coatings to learn more about the nano-crystalline
or amorphous phases formed. By the mentioned means we suc-
ceeded to detect two modifications of zinc selenide and one
modification of copper selenide formed on the copper substrate
along with amorphous elemental selenium during the electrode-
position of ZnSe.
C3
-0.62 V
Fig. 1. Cyclic voltammogram for Cu electrode in solution (mol dm−3): 0.2 ZnSO4,
0.002 H2SeO3, pH 2.0, T = +30 ◦C. Potential scan rate 20 mV s−1
.
authors [13,14]. The most positive cathodic peak is attributable to
the electrodeposition of Se according to the equation:
H2SeO3 + 4H+ + 4e− = Se + 3H2O
(2)
However, Eq. (1) mentioned in the Introduction section should
be taken into account. A shift of cathodic peak C1 to positive poten-
tials during further cycling reported by Kowalik and Fitzner [14]
could be caused by the formation of Cu2Se during the first cycle.
To verify if reaction (1) takes place potentiostatic deposition was
carried out at potential C1 during 60 min and the XRD pattern of the
deposit obtained was measured immediately after the deposition.
The XRD pattern (Fig. 2) proves copper selenide to be formed during
Se electrodeposition on the copper substrate. Nearly all the XRD
peaks on the pattern match fairly well with those presented in PDF
file no. 47-1448 for orthorhombic Cu2Sex. No peaks attributable to
elemental Se can be seen on the pattern. Nevertheless it could be
supposed that some amount of elemental selenium was present in
an amorphous state.
The quantity of Cu2Sex increased with electrodeposition time.
Fig. 3 presents a ratio of integral intensity of XRD peak of Cu2Sex at
2ꢁ ≈ 51.9◦ to that of Cu 200 as a function of the deposition time.
An increasing quantity of the Cu2Sex with deposition time could
mean that rather fast diffusion of Se into Cu takes places even at
a temperature of +30 ◦C. The ratio increased yet more 3 days after
deposition for samples deposited during 20 and 40 min though it
remained constant for that deposited during 60 min. That could be
caused by further diffusion of the deposited amorphous selenium
into the copper substrate even when the deposition has finished.
It is in agreement with the results of other researchers and proves
that amorphous selenium diffuses into copper [20]. However,
there is a certain limit of the diffusion depth as for the sample
2. Experimental
The electrodeposition was carried out (1) potentiostatically, (2)
applying cyclic potential scanning in an appropriate potential range
(3) using pulses of different potential and duration. Parameters of
the two latter approaches will be indicated when presenting the
results obtained. A potentiostat PI-50-1.1 connected with PC was
used for control and data acquisition.
An electrolyte solution of optimal composition (0.2 mol dm−3
ZnSO4 and 0.002 mol dm−3 H2SeO3 [13]) was prepared using triply-
distilled water and analytical grade reagents. The pH of the solution
was adjusted to 2.0 using H2SO4 and a temperature of +30 0.5 ◦C
was maintained. A three-compartment glass electrolytic cell was
used. A copper foil of 1 × 1 cm2 geometrical area was used as a
working electrode, which prior to electrodeposition was chemi-
cally etched in a 1:1:1 volume ratio mixture of acids: HNO3, H3PO4,
CH3COOH and next rinsed with a stream of triply-distilled water.
A Cu–Sn layer on Mo was electrodeposited in a citrate solution
containing 0.02 mol dm−3 CuSO4 and 0.01 mol dm−3 SnSO4. A Pt
(purity 99.995) plate of 1.5 × 2 cm2 geometrical area was used as
a counter electrode. Ag/AgCl/KCl (saturated) was used as a refer-
ence electrode and all potentials are given versus this electrode.
The electrolyte solution was purged by Ar 5.0 gas for 1 h prior to
electrodeposition and it was kept purging during the deposition.
A phase composition of the deposits was examined by an X-
ray diffractometer D8 Advance (Bruker AXS) with Cu K␣ radiation
˚
(ꢀ = 1.54183 A, Ua = 40 kV, Ia = 40 mA) separated by a curved multi-
layer monochromator mounted on the primary beam. Symmetrical
ꢁ/2ꢁ geometry and grazing incidence (GIXRD) techniques were
used and in the latter case the incidence angle (ꢁ angle) was 0.5◦.
The XRD patterns were measured in 2ꢁ range from 10 to 60◦ in a
step scan mode: a step size (ꢂ2ꢁ) 0.04◦, counting duration 5 s.
The surface morphology and chemical composition were exam-
ined by a scanning electron microscope Helios Nanolab 650 (FEI
company) with EDX (Oxford instruments).
200
Cu2Sex PDF 47-1448
Cu PDF 08-0836
150
100
50
0
The photoelectrochemical response was measured in a home-
made cell in a 0.2 mol dm−3 aqueous solution of K2SO4. The
measurement technique is presented elsewhere [19].
10
20
30
40
50
60
3. Results and discussions
2Θ / degrees
Cyclic voltammograms shown in Fig. 1 have the same character-
istic cathodic and anodic peaks which have been reported by other
Fig. 2. XRD pattern for the deposit obtained on the Cu cathode at potential of C1
(−0.08 V vs. Ag/AgCl).

120
R. Jusˇke˙ nas et al. / Electrochimica Acta 70 (2012) 118–123
200
5
4
3
2
1
Cu PDF 08-0836
ZnSe PDF 37-1463
150
100
50
after 3days
as-deposited
0
10
20
30
40
50
60
2Θ / degrees
20
30
40
50
60
Fig. 5. XRD pattern for the deposit obtained on the Cu cathode at potential of C2
(−0.48 V vs. Ag/AgCl).
t / min
Fig. 3. Ratio of intensity of the XRD peak Cu2Sex at 2ꢁ of 51.9◦ to that of Cu 200 as
a function of deposition time.
Fig. 6 presents the XRD pattern (black solid curve) for deposit
obtained at the potential of cathodic peak C3 (−0.62 V) during
60 min. The pattern looks close to that of the coating electrode-
posited at the potential of −0.48 V, however the XRD peaks of
ZnSe are of higher intensity. The ZnSe is obviously nano-crystalline.
An appropriate procedure of recrystallization can significantly
improve the crystallinity of a nano-crystalline material and, conse-
quently, the quality of XRD pattern. Fig. 6 presents the XRD pattern
(red thin curve) for the same deposit after annealing at +300 ◦C in
Ar atmosphere for 3 h. Very sharp XRD peaks appeared on the pat-
tern of the annealed sample and they apparently corresponded to
cubic ZnSe, orthorhombic Cu2Sex and Cu. A small amount of ZnO
(PDF no. 36-1451) was also present. The results obtained can be
explained assuming that at a potential of −0.62 V along with forma-
tion of ZnSe the electrodeposition of Se and insertion of amorphous
Zn(OH)2 took place. While annealing the latter two phases were
transformed into Cu2Sex and ZnO, respectively. The presence of Se
phase in the as-deposited ZnSe coating was confirmed by EDX: the
quantity of Se was higher by 8–15 at.% compared with that of Zn in
the deposit (Table 1).
deposited during 60 min the intensity ratio does not significantly
change with the aging time.
The above presented assumptions can get one more evidence if
compare the ratio of the integral intensity of XRD peak of Cu2Sex at
2ꢁ ≈ 51.9◦ measured by GIXRD to that obtained using ꢁ/2ꢁ geom-
etry (Fig. 4). The first intensity depicts the quantity of Cu2Sex at the
surface of Cu electrode and the second one in the bulk of it. The ratio
decreases with deposition time indicating that the layer of Cu2Sex
becomes thicker. The thickness of the layer increases also with the
aging time.
The XRD patterns for the deposits obtained at more negative
potentials (−0.2 and −0.4 V) look quite similar to that shown in
Fig. 2.
Fig. 5 shows the XRD pattern for the coating electrodeposited at
the potential of cathodic peak C2 (−0.48 V) during 60 min. Three
broad and two narrow XRD peaks are seen on the pattern. The
broad ones match well with those presented in PDF no. 37-1463
for cubic ZnSe and the narrow ones correspond to copper (PDF no.
04-0836). Such broad XRD peaks of ZnSe are indicative of a nanos-
tructured material. The crystallite size of ZnSe in crystallographic
direction ꢀ1 1 1ꢁ was calculated using Scherrer equation and was
equal to 3.7 0.8 nm. The increase in quantity of selenious acid in
the electrolyte solution up to 0.01 mol dm−3 shifts the potential of
cathodic peak C2 to a more negative potential −0.52 V and it results
in an increase in the quantity of electrodeposited ZnSe.
SEM images of deposits electrochemically formed on the Cu
electrode at different potentials (E = −0.08 V, left-side images, and
E = −0.62 V, right-side images) are shown in Fig. 7. The deposit
obtained at E = −0.08 V presents disk-like agglomerates of Cu2Sex
crystallites according to XRD data (Fig. 2). Most of the disks are
perpendicular to the electrode surface. Results of EDX measure-
ments of the deposits are shown in Table 1. No zinc was detected in
600
3,0
ZnSe PDF 37-1463
as deposited
after 3 days
Cu PDF 08-0836
Cu Se PDF 47-1448
2
x
2,5
ZnO PDF 36-1451
400
200
0
2,0
1,5
1,0
0,5
annealed
as-deposited
25
30
35
40
45
50
55
20
30
40
50
60
2Θ / degree
t / min
Fig. 6. XRD pattern for the deposit formed on the Cu cathode at potential of C3
(−0.62 V vs. Ag/AgCl). (For interpretation of the reference to color in the text for Fig.
6, the reader is referred to the web version of the article.)
Fig. 4. Ratio of intensity of the XRD peak Cu2Sex at 2ꢁ of 51.9◦ measured in the
GIXRD geometry to that obtained in ꢁ/2ꢁ one as a function of deposition time.

R. Jusˇke˙ nas et al. / Electrochimica Acta 70 (2012) 118–123
121
Table 1
Chemical composition of deposits electrochemically formed on Cu cathode in solution containing 0.2 mol dm−3 of ZnSO4 and 0.002 mol dm−3 of H2SeO3.
E (V)
Examined area notation
Cu (at.%)
Se (at.%)
Zn (at.%)
−0.08
−0.08
−0.62
−0.62
−0.62
1
2
3
4
5
72.2 4.5
78.6 4.5
51.7 2.5
53.9 2.5
37.1 2.5
27.8 4.5
21.4 4.5
27.8 2.5
29.0 2.5
39.3 2.5
–
–
20.5 3.3
17.1 3.3
23.6 3.3
Fig. 7. SEM images of deposits formed at potential of C1 (left-side images) and of C3 (right-side images).
the deposits obtained at E = −0.08 V. The quantity of Se measured
from a larger area (assigned “1” on left-side lower image, Fig. 7)
was slightly lower since this area contains more dark spots which
could be holes in the deposit layer. The deposit of ZnSe (right side
images, Fig. 7) mostly presents globular agglomerates of ZnSe crys-
tallites whose size should be 3–5 nm according to the broad XRD
peaks of ZnSe (Fig. 6). Bright particles (assigned “3” and “4” on the
right-side lower image, Fig. 7) emerging on the top of darker glob-
ular agglomerates (assigned “5” on right-side lower image, Fig. 7)
contains a larger quantity of Se (Table 1). These particles could be
crystalline selenium, however it was not confirmed by XRD due to
a small quantity of these particles.
In attempt to discover the origin of anodic peaks A1 and A2
(Fig. 1) electrodeposition was carried out using cyclic potential
scanning forwards and backwards in the potential range from −0.4
to −0.62 V, i.e. from the potential of anodic peak A1 to that of
cathodic C3. It was suggested that such deposition should yield
a relative increase in the quantity of the substance which elec-
trochemically dissolves at the potential of anodic peak A2 [4,18].
The cycling with a potential scan rate of 10 mV s−1 proceeded for
60 min. Fig. 8 shows an XRD pattern of the coating electrodeposited
using the above described approach. It can be clearly seen that
the XRD peak ZnSe 1 1 1 became sharper if compared with that in
Fig. 6 (FWHM equaled 1.1◦ and 2.6◦, respectively) and small knolls
appeared on the both shoulders of this peak (marked with “?” sym-
bols on Fig. 8). These features could indicate that at the anodic
potential of A1 the nano-crystalline fraction of cubic ZnSe was dis-
solved making the XRD peak ZnSe 1 1 1 sharper and small peaks of
some other phase more distinct.
It could be supposed that the phase, which became detectable in
Fig. 8 (upper red curve) should dissolve at a more positive potential
of anodic peak A2. So the same cyclic potential scanning approach
250
E from -0.62 to -0.31 V
E from -0.62 to -0.40 V
200
?
150
100
50
?
0
24
26
28
30
32
2Θ / degrees
Fig. 8. XRD pattern for the deposit formed on the Cu cathode by cyclic potential
scanning. The potential scan rate 10 mV s−1
.

122
R. Jusˇke˙ nas et al. / Electrochimica Acta 70 (2012) 118–123
Sn
Mo
Cu
100
200
150
100
50
ZnSe PDF no 37-1463
ZnSe PDF no 89-2940
Sn
6,26
5
Se
ZnSe
γ−CuSe
50
0
0
20
30
40
50
60
24
26
28
30
32
2
Θ / degrees
2
Θ
/ degrees
Fig. 9. XRD pattern for the deposit formed on the Cu cathode by pulse electrodepo-
sition: E1 = −0.62 V, t = 10 s; E2 = −0.31 V, t = 8 s.
Fig. 11. XRD pattern for the ZnSe deposit formed on the Cu–Sn cathode. Sn – PDF no.
04-0673; Mo – PDF no. 42-1120; Cu6,26Sn5 – PDF no. 47-1575; Se – PDF no. 06-0362;
ZnSe – PDF no. 37-1463; ␥-CuSe – PDF no. 27-0185.
was ≥530 nm. For the wavelength of 505 nm the difference of
open-circuit potential reached +20 mV and for that of 455 nm
+38 mV indicating that the ZnSe deposit was a p-type semicon-
ductor with a band-gap of about 2.5–2.7 eV.
was employed for the potential range from −0.31 to −0.62 V. The
ZnSe peaks remained sharp as in the previous case and the knolls on
the shoulders of XRD peak ZnSe 1 1 1 became less visible, especially
the one on the right shoulder (Fig. 8, lower black curve). It could be
inferred that the assumption regarding dissolution of the unknown
phase was confirmed.
According to Kowalik et al. [13] anodic peak A2 could be related
to the process of desorption of species adsorbed during potential
scan in the cathodic direction. To reduce quantity of the adsorbed
species, a pulse electrodeposition was tried in attempt to find out
the origin of the unknown phase. Short pulses of two potentials
were repeatedly used for 60 min. The first pulse was at potential
E1 = −0.62 V, with duration t = 10 s and the second one at that of
−0.31 V, t = 8 s. Fig. 9 shows an XRD pattern of the coating electrode-
posited using the above described approach. Two distinct peaks
appeared on the both sides of XRD peak ZnSe 111 and they are
attributable to the hexagonal ZnSe phase (PDF no. 89-2940). The
result obtained infers that usage of short pulses make it possible
to more effectively remove the adsorbed species which results in
formation of ZnSe of a better crystallinity.
The photoelectrochemical response of ZnSe electrodeposited at
a potential of −0.62 V is shown in Fig. 10. The response of electro-
chemical system to the optical perturbation was investigated by
recording the dynamics of the photopotential under open-circuit
conditions. Light diodes emitting light of different wavelength
(indicated in Fig. 10) were used in sequence to illuminate the ZnSe
surface and the open-circuit potential corresponding to different
wavelength was measured. The potential difference for dark and
illuminated ZnSe was 3–5 mV only until the light wavelength
As the first attempt to use the electrodeposition of ZnSe for fab-
rication of Cu2ZnSnSe4 for a thin film solar cell ZnSe was deposited
on the electrodeposited Cu–Sn coating, which contained 65 at.% of
Cu and 35 at.% of Sn according to EDX data. The cyclic voltammo-
gram for the Cu–Sn electrode is shown in Fig. 1 (dashed curve). It
was slightly different from that for the Cu electrode: there was no
cathodic peak C1 and the peak C3 was broader. According to Kowa-
lik and Fitzner [14] the cathodic peak C1 is related to the interaction
between selenium and copper during the deposition process. In the
case of the Cu–Sn substrate copper selenide most probably did not
form since the substrate did not contain a pure Cu phase (Fig. 11).
On the other hand, it was shown by Lukinskas et al. [21] that the
interaction of Se with Sn is very slow at room temperature. When
electrodeposition of Se proceeded only according to reaction (2) a
layer of grey electro-inactive Se was forming [14]. Those could be
the reasons due to which a slow increase in cathodic current was
seen instead of the peak C1 in the cyclic voltammogram when the
Cu–Sn substrate was used.
Fig. 11 shows the XRD pattern of as-deposited ZnSe on the layer
of Cu–Sn electrodeposited on the Mo coated glass substrate. Along
with peaks of Cu6.25Sn5 (PDF no. 47-1575), Sn (PDF no. 06-0362)
ZnSe
SnSe
100
ε−Cu Sn
3
Mo
-0.110
90 mW cm-2
-0.115
10
-0.120
light off
-0.125
1
20
-0.130
-0.135
light on
627 nm
30
40
/ degrees
50
60
455 nm
505 nm
2Θ
617 nm
590 nm
530 nm
Fig. 12. XRD pattern for the ZnSe electrodeposited on the Cu–Sn cathode and
annealed for 0.5 h in Ar atmosphere at +500 ◦C. SnSe – PDF no. 48-1224; ␧-Cu3Sn
PDF no. 01-1240.
Fig. 10. Dependence of open circuit potential of the electrodeposited ZnSe on the
wavelength of the illumination.

R. Jusˇke˙ nas et al. / Electrochimica Acta 70 (2012) 118–123
123
and Mo (PDF no. 42-1120) quite distinct peaks of ZnSe and Se (PDF
Acknowledgment
no. 06-0362) are present. The presence of Cu2Se is not apparent:
only a broad peak at 2ꢁ of ∼13◦ (not shown in Fig. 11) and a hump
on the left side of peak ZnSe 1 1 1 could indicate the presence of it.
Some peaks are attributable to ␥-CuSe (PDF no. 27-0185).
Fig. 12 presents the XRD pattern of the previous sample after
annealing at +500 ◦C in Ar atmosphere for 0.5 h. The pattern proves
that SnSe (PDF no. 48-1224) was formed during the annealing. It
is obvious that the quantity of Se in the deposit was insufficient
to transform all the copper and tin into selenides since XRD peaks
of ␧-Cu3Sn (PDF no. 01-1240) were well seen. Though Cu2ZnSnSe4
was not formed in the current experiment it can be supposed that
kesterite is formed when annealing is carried out in Se or H2Se
atmosphere. And while using S or H2S atmosphere during annealing
a mixed S–Se kesterite with even better photovoltaic characteristics
can be formed.
This research was funded by a grant (no. ATE-07/2010) from the
Research Council of Lithuania.
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