Influence of nanostructured ITO films on surface recombination processes in silicon solar cells
This paper describes the results of comparative studies of illumination currentvoltage characteristics and spectral characteristics of silicon solar cells with rear location of the collector p-n-junction for the cases of non-passivated and passivated front illuminated surface. Passivation was perfor...
Gespeichert in:
| Datum: | 2015 |
|---|---|
| Hauptverfasser: | , , , , , , |
| Format: | Artikel |
| Sprache: | English |
| Veröffentlicht: |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2015
|
| Schriftenreihe: | Semiconductor Physics Quantum Electronics & Optoelectronics |
| Online Zugang: | http://dspace.nbuv.gov.ua/handle/123456789/121277 |
| Tags: |
Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Zitieren: | Influence of nanostructured ITO films on surface recombination processes in silicon solar cells / V.P. Kostylyov, A.V. Sachenko, O.A. Serba, T.V. Slusar, V.M. Vlasyuk, P.O. Tytarenko, V.V. Chernenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 4. — С. 464-467. — Бібліогр.: 9 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-121277 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-1212772017-06-14T03:07:50Z Influence of nanostructured ITO films on surface recombination processes in silicon solar cells Kostylyov, V.P. Sachenko, A.V. Serba, O.A. Slusar, T.V. Vlasyuk, V.M. Tytarenko, P.O. Chernenko, V.V. This paper describes the results of comparative studies of illumination currentvoltage characteristics and spectral characteristics of silicon solar cells with rear location of the collector p-n-junction for the cases of non-passivated and passivated front illuminated surface. Passivation was performed by silicon dioxide layer or ITO layer. It was found that ITO layer surface passivation with formation of ITO/silicon heterojunction, unlike silicon dioxide layer passivation, leads to a significant reduction of the effective surface recombination velocity. It significantly increases the value of the internal quantum efficiency in the wavelength range from 550 to 1050 nm and, as a result, significantly increases the value of short-circuit current of solar cells. 2015 Article Influence of nanostructured ITO films on surface recombination processes in silicon solar cells / V.P. Kostylyov, A.V. Sachenko, O.A. Serba, T.V. Slusar, V.M. Vlasyuk, P.O. Tytarenko, V.V. Chernenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 4. — С. 464-467. — Бібліогр.: 9 назв. — англ. 1560-8034 DOI: 10.15407/spqeo18.04.464 PACS 72.20.Jv, 73.50.Gr, 78.67.-n, 88.40.jj http://dspace.nbuv.gov.ua/handle/123456789/121277 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| description |
This paper describes the results of comparative studies of illumination currentvoltage characteristics and spectral characteristics of silicon solar cells with rear location of the collector p-n-junction for the cases of non-passivated and passivated front illuminated surface. Passivation was performed by silicon dioxide layer or ITO layer. It was found that ITO layer surface passivation with formation of ITO/silicon heterojunction, unlike silicon dioxide layer passivation, leads to a significant reduction of the effective surface recombination velocity. It significantly increases the value of the internal quantum efficiency in the wavelength range from 550 to 1050 nm and, as a result, significantly increases the value of short-circuit current of solar cells. |
| format |
Article |
| author |
Kostylyov, V.P. Sachenko, A.V. Serba, O.A. Slusar, T.V. Vlasyuk, V.M. Tytarenko, P.O. Chernenko, V.V. |
| spellingShingle |
Kostylyov, V.P. Sachenko, A.V. Serba, O.A. Slusar, T.V. Vlasyuk, V.M. Tytarenko, P.O. Chernenko, V.V. Influence of nanostructured ITO films on surface recombination processes in silicon solar cells Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Kostylyov, V.P. Sachenko, A.V. Serba, O.A. Slusar, T.V. Vlasyuk, V.M. Tytarenko, P.O. Chernenko, V.V. |
| author_sort |
Kostylyov, V.P. |
| title |
Influence of nanostructured ITO films on surface recombination processes in silicon solar cells |
| title_short |
Influence of nanostructured ITO films on surface recombination processes in silicon solar cells |
| title_full |
Influence of nanostructured ITO films on surface recombination processes in silicon solar cells |
| title_fullStr |
Influence of nanostructured ITO films on surface recombination processes in silicon solar cells |
| title_full_unstemmed |
Influence of nanostructured ITO films on surface recombination processes in silicon solar cells |
| title_sort |
influence of nanostructured ito films on surface recombination processes in silicon solar cells |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2015 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/121277 |
| citation_txt |
Influence of nanostructured ITO films on surface recombination processes in silicon solar cells / V.P. Kostylyov, A.V. Sachenko, O.A. Serba, T.V. Slusar, V.M. Vlasyuk, P.O. Tytarenko, V.V. Chernenko // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 4. — С. 464-467. — Бібліогр.: 9 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
| work_keys_str_mv |
AT kostylyovvp influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells AT sachenkoav influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells AT serbaoa influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells AT slusartv influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells AT vlasyukvm influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells AT tytarenkopo influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells AT chernenkovv influenceofnanostructureditofilmsonsurfacerecombinationprocessesinsiliconsolarcells |
| first_indexed |
2025-07-08T19:31:07Z |
| last_indexed |
2025-07-08T19:31:07Z |
| _version_ |
1837108373775974400 |
| fulltext |
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 464-467.
doi: 10.15407/spqeo18.04.464
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
464
PACS 72.20.Jv, 73.50.Gr, 78.67.-n, 88.40.jj
Influence of nanostructured ITO films on surface recombination
processes in silicon solar cells
V.P. Kostylyov, A.V. Sachenko, O.A. Serba, T.V. Slusar, V.M. Vlasyuk,
P.O. Tytarenko, V.V. Chernenko
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect Nauky, 03028 Kyiv, Ukraine;
Phone/fax: +38 (044) 525 5788. E-mail: vkost@isp.kiev.ua
Abstract. This paper describes the results of comparative studies of illumination current-
voltage characteristics and spectral characteristics of silicon solar cells with rear location
of the collector p-n-junction for the cases of non-passivated and passivated front
illuminated surface. Passivation was performed by silicon dioxide layer or ITO layer. It
was found that ITO layer surface passivation with formation of ITO/silicon
heterojunction, unlike silicon dioxide layer passivation, leads to a significant reduction of
the effective surface recombination velocity. It significantly increases the value of the
internal quantum efficiency in the wavelength range from 550 to 1050 nm and, as a
result, significantly increases the value of short-circuit current of solar cells.
Keywords: solar cell, internal quantum efficiency, external quantum efficiency, velocity
of surface recombination, spectral dependence, isotype heterojunction.
Manuscript received 23.04.15; revised version received 14.08.15; accepted for
publication 28.10.15; published online 03.12.15.
1. Introduction
Films of transparent conductive oxides (TCO)
characterized by high optical transparence and electrical
conductivity are now widely used in manufacturing up-
to-date optoelectronic devices, where they are applied
for creation of transparent electrodes and antireflection
layers. When using these films in silicon solar cells
(SC), it is also important to solve the task of passivation
of silicon surface with the aim to reduce the velocity of
surface recombination and, as a result, to enhance the
efficiency of these elements. In particular, firms
Sanyo/Panasonic already use TCO films in industrial
production of silicon SC based on the junction а-
Si:H/Si(crystalline), which reach the efficiency up to
25.6% [1]. One of the diverse TCO materials is indium
oxide doped with tin ITO that, starting from 1954, when
ITO film with suitable combination of optical
transparence and electrical conductivity was prepared
[2], is actively investigated with the aim of large-scale
usage [3, 4].
On the other hand, it is wellknown that, to decrease
the negative influence of surface recombination on
performances of silicon SC, beside the method for
passivation of silicon surface, widely used is the method
for creation of near-surface junctions. While passivation
of the silicon surface, which is realized by deposition of
dielectric layers, decreases the velocity of surface
recombination directly at the interface silicon-dielectric
due to lowering the concentration of surface
recombination centers, availability of of near-surface
junctions provides a potential barrier that limits the
influx of definite type charge carriers to surface
recombination centers [5]. These near-surface junctions
can be created due to formation of both isotype n
+
-n- or
р
+
-р-junctions and floating р
+
-n- or n
+
-р-junctions [6,7]
near the surface. In the case of available near-surface
junctions, researches operate with the notion of
mailto:vkost@isp.kiev.ua
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 464-467.
doi: 10.15407/spqeo18.04.464
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
465
“effective surface recombination velocity” related to the
boundary between the range of space charge and quasi-
neutral bulk. At the same time, this decrease in the
negative influence of surface recombination on silicon
SC performances is studied insufficiently.
Therefore, this work was aimed at performing
investigations of the efficiency of applied ITO layers for
creation of the junction ІТО/Si with the purpose to
decrease both recombination (effective surface
recombination velocity) and optical (coefficient of light
reflection) losses in silicon SC.
2. Experimental methods
Experimental investigations were performed using
the SC samples with rear collector junction having the
thiockness 400 µm. The samples were made from zone
melting n-type silicon КБЕ-2 with the specific resistance
close to 2 Ohmcm. These samples had the frontal
surface free of electrodes. It was provided by placing the
aluminum contact metalization of the interdigital type on
the rear surface of SC in the form of oppositely directed
combs, when one of them provides contact to the base n-
range of SC, while the other – to the р
+
-range created
due to boron diffusion near the rear surface. Near the
frontal surface, these SC had shallow isotype n
+
-n-
junction formed using phosphorus diffusion at the
doping level approximately 10
19
cm
-3
in the n
+
-layer.
Besides, to provide surface passivation and lowering
optical losses, the frontal surface of SC was covered
with the layer of silicon dioxide of 110-nm thickness.
The schematic view of the silicon SC with the rear
placement of the collecting р-n-junction and anti-
recombination n
+
-n-junction is shown in Fig. 1.
The abovementioned SC samples served as the
objects for investigations of light current-voltage
characteristics (CVC), and the latter enabled to
Fig. 1. Schematic representation of back junction, rear contact
experimental silicon SC.
determine the main photo-energetic characteristics of
SC. Also, they allowed measuring the spectral
dependences of the short-circuit current Іsc through SC
within the wavelength range ∆λ = 400…1200 nm. These
dependences were measured in the mode of automatic
tuning the level of irradiance, which enabled to obtain
the spectra of internal and external efficiencies. To
determine the influence of the ІТО/Si heterojunction
formed on the front surface of SC on generation-
recombination processes in it, the above characteristics
were studied step-by-step, namely: first, for initial SC,
then after removing the silicon dioxide layer from the
front surface (by using the treatment in the concentrated
fluorine acid) and, finally, after formation of a
heterojunction at the surface of silicon SC by deposition
of the ITO film with the thickness 75 nm, applying the
method of reactive ion sputtering the indium-tin target in
argon-oxygen ambient. When processing in concentrated
fluorine acid, SC were reliably protected, etchant was
active only on the frontal surface. After processing, the
samples were thoroughly washed in deionized water.
Such a choice of the experimental samples with the
rear placement of barriers and contact metallization was
related with their high sensitivity to surface and bulk
recombination, changes of which we should register.
Light CVC, in particular, allow studying behavior
of the short-circuit current, the value of which is defined
by the efficiency of collection inherent to photo-
generated charge carriers, and using the spectral
dependences of the short-circuit current one can
determine spectra of internal and external quantum
efficiencies. The latter enables one to ascertain features
of recombination processes at the near-surface range and
in bulk, which, in turn, make an effect on the efficiency
of collection of non-equilibrium charge carriers in SC.
Our measurements of light CVC and spectral
dependences were performed using the equipment for
photo-technical testing SC as well as installation for
determination of relative spectral characteristics of photo-
converters in the Photovoltaic Converters and Modules
Test Center at V.Ye. Lashkaryov Institute of
Semiconductor Physics, NAS of Ukraine.
The refraction index and thickness of ITO films
were determined using a laser ellipsometer at the
wavelength 632.8 nm.
3. Results and discussion
Shown in Fig. 2 are typical light CVC of the studied SC
obtained under the spectral conditions АМ1.5 (irradiance
РL = 1000 W/m
2
, temperature Т = 25
0
С) starting from the
initial one to the following after removing the silicon
dioxide layer and after depositing the ITO film. The
values of SC photoelectric parameters determined using
these light CVC are adduced in Table 1. And Fig. 3 shows
the spectral dependences of internal quantum efficiency of
the same SC after identical treatment stages.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 464-467.
doi: 10.15407/spqeo18.04.464
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
466
Illuminated VA characteristics
0
5
10
15
20
25
0 0.1 0.2 0.3 0.4 0.5 0.6
V, V
І,
m
А
1-Init
2-HF
3-ITO
ITO +62% !!!
HF -15,5%
Init1
2
3
Fig. 2. Light current-voltage characteristics of SC at different
stages of research: initial SC(1), after removing the SiO2 layer
(2) and after formation of the ITO/Si heterojunction.
Table 1.
Light CVC
(Fig. 2)
Short-
circuit
current,
Іsc, mA
Open-
circuit
voltage,
Voc, V
Fill
factor
of light
CVC, Kf
Initial 16.43 0.515 0.75
After removing
the SiO2 layer
13.89 0.521 0.75
After deposition
of the ІТО film
22.43 0.527 0.75
Internal quantum efficiency IQE
0
0.1
0.2
0.3
0.4
0.5
400 600 800 1000 1200
Wavelength, nm
1 - init
2 - HF
3 - ITO
1
3 2
1,2
Fig. 3. Spectral dependencies of internal quantum efficien-
cies – IQE of SC obtained at different stages of researches:
initial SC (1), after removing the SiO2 layer (2) and after
formation of the ITO/Si heterojunction.
Our ellipsometric investigations have shown that
ITO films are characterized by the values of refraction
index lying within the range n = 1.95…2.0, while the
thickness is close to 75 nm. This thickness was chosen
with account of optimal reduction of light reflection
from silicon surface under conditions AM 1.5.
As seen from Fig. 2 and Table 1, removing the
SiO2 layer from the frontal surface of SC results in
decreasing the short-circuit current Іsc by the value
approximately 15.5%, while deposition of the ITO film –
to considerable growth of this parameter. The short-
circuit current value in the sample with ITO film
exceeds that for SC with the removed silicon dioxide
layer by approximately 62% and is considerably higher
than the value for the initial SC sample having the SiO2
layer on its frontal surface. In this case, the open-circuit
voltage is monotonically increased from 515 mV in the
initial sample up to 527 mV after deposition of the ITO
layer. It should be noted that for all the stages of
experiment the fill factor FF of light CVC was kept
unchanged and remained the same as that for the initial
light CVC, namely 0.75.
Spectral dependences of the internal quantum
efficiency (IQE) at various stages of investigations
changed as follows from Fig. 3. At the very beginning,
after removing the silicon dioxide layer from the SC
front surface, there takes place a weak increase of the
internal quantum efficiency only near the maximum of
dependence, and then, after deposition of the ITO layer
on this surface, the IQE spectral characteristics is
essentially changed as compared with previous
dependences. It is pronounced in the considerable
increase of the internal quantum efficiency within the
wavelength range 550…1050 nm and near the maximum
of characteristic, in particular. It should be noted that
light reflection has no influence on IQE values, since in
the case of non-absorbing layers
R
EQE
IQE
1
,
where EQE is the external quantum efficiency, and R –
reflection coefficient of the SC surface.
Similar results were observed in all the studied SC.
It is known that the value of surface recombination
velocity for the non-passivated silicon surface
considerably exceeds the respective value for the system
Si-SiO2. But the found changes in the short-circuit
current values after removing the SiO2 layer are
indicative of the fact that these changes are caused just
by varying optical characteristics of the SC front surface
(i.e., removal of the antireflection coating), while any
change in the value of effective velocity of surface
recombination Seff, valid for the boundary between the
space charge region and quasi-neutral bulk, is not
observed. It is confirmed by practical absence of
changes in respective spectral dependences for the
internal quantum efficiency. We believe that it is caused
by availability of the isotype n
+
-n-junction at the SC
front surface.
The found in this work approximately 62%
increase in the value of Isc current after deposition of
ITO layer on the SC frontal surface and formation of the
heterojunction ITO/silicon cannot be explained only by
improvement of optical characteristics inherent to the SC
frontal surface. It means that there takes place a
considerable decrease in the value of effective surface
recombination velocity Seff. It is unambiguously
confirmed by the considerable increase in the internal
quantum efficiency within the wavelength range
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 4. P. 464-467.
doi: 10.15407/spqeo18.04.464
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
467
550…1050 nm, which is clearly seen from juxtaposition
of the spectral dependences obtained for the SC samples
before and after deposition of ITO layer (Fig. 3).
Treatment of the experimental dependences IQE() by
using the method [9] has shown that, after formation of
the heterojunction ITO/silicon, there takes place
approximately 3-fold decrease in the value of effective
surface recombination velocity. More exact ascertaining
all the mechanisms responsible for the decrease of this
value Seff after deposition of ITO layer requires
additional theoretical investigations that are now
performed.
4. Conclusions
It has been founded experimentally that effective surface
recombination velocity Seff both on the passivated by
thermal SiO2 film front surface with isotype n + -n
junction of the back junction back contacts SC, and after
its removal remains approximately constant. At the
same time, formation of the ITO/silicon heterojunction
on this surface results in considerable decrease of Seff
and, consequently, in essential growth of the internal
quantum efficiency value within the wavelength range
550…1050 nm.
References
1. K. Masuko, M. Shigematsu, T. Hashiguchi, D.
Fujishima, M. Kai, N. Yoshimura, T. Yamaguchi,
Y. Ichihashi, T. Yamanishi, T. Takahama, M.
Taguchi, E. Maruyama, S. Okamoto. Achievement
of more than 25% conversion efficiency with
crystalline silicon heterojunction solar cell//IEEE
Journal of Photovoltaics 4, p.1433–1435 (2014).
2. G. Rupprecht. Untersuchungen der elektrischen
und lichtelektrischen Leitfähigkeit dünner
Indiumoxydschichten // Z. Phys. 139 (5), p. 504-
517 (1954).
3. N. Balasubramanian and A. Subrahmanyam,
“Electrical and Optical Properties of Reactively
Evaporated Indium Tin Oxide (ITO) Films -
Dependence on Substrate Temperature and Tin
Concentration”, Journal of Physics D: Applied
Physics, 22, p. 206 – 209 (1989).
4. J. C. C. Fan and J. B. Goodenough, “X-Ray
Photoemission Spectroscopy Studies of Sn doped
Indium Oxide Films”Journal of Applied Physics,
48(8), p. 3524 – 3531 (1977)
5. A.P. Gorban, V.P. Kostylyov, A.V. Sachenko et al.
Impact of Excess Charge Carrier Concentration on
Effective Surface Recombination Velocity in
Silicon Photovoltaic Structures // Ukr. J. Phys.
51(6), p. 598-604 (2006)..
6. M.I. Yernaux, C. Battocchio, P. Verlinden, F. Van
De Wiele. A one-dimensional model for the
quantum efficiency of front-surface-field solar
cells// Solar Cells. 13, p. 83-97 (1984).
7. W.P. Mulligan, D.H. Rose, M.J. Cudzinovic et al.
Manufacture of Solar Cells with 21% Efficiency //
Proc. 19th European Photovoltaic Solar Energy
Conf. - Paris, France, 2004. P. 387-390.
8. A.P. Gorban, V.P. Kostylyov, A.V. Sachenko,
O.A. Serba, I.O. Sokolovskyi, V.V. Chernenko.
Effect of Floating p–n Junctions on the Efficiency
of Silicon Back Side Contact Solar Cells // Ukr. J.
Phys. 55(7), p.783-790 (2010).
9. V.P. Kostylyov, V.G. Litovchenko, A.V. Sachenko,
T.V. Slusar, V.V. Chernenko. Features of solar
cells and solar silicon wafers surface photovoltage
spectral dependences in the short-wave absorption
region. Proceedings 28 European Photovoltaic
Solar Energy Conf. and Exhibition, Paris, France,
30 Sept. - 04 Oct., 2013.- Р.1715-1718.
|