INTERNATIONAL CONFERENCE ON SOLAR ENERGY PHOTOVOLTAIC (ICSEP – 2012) A- SILICON PV: S-2
Improvement of the Performance of Single Junction
a-Si Integrated Mini Modules with Oxide Based
U. Basavaraju2, Gourab Das1, Rajive Tomy M2, Chandan Banerjee2, Sumita Mukhopadhyay1, A.K.Barua1*,
1Centre of Excellence for Green energy and Sensor Systems, Bengal Engineering and Science University,
2Hind High vacuum Co. Pvt. Ltd. Phase I, Peenya Industrial Area, Bengaluru, India, 560058
(a-SiO) is a better photovoltaic material than a-SiC [10-12].
Abstract- We have developed oxide based window layer, buffer
Most of the oxygen atoms are bonded in Si – O – Si form and
layer and n-layer by radio frequency plasma enhanced chemical
partly in Si – OH form. It is more electronegative than that of
vapour deposition method for use in the fabrication of single
Si or OH. So while this oxygen gets bonded to Si atom the
junction amorphous silicon (a-Si) integrated mini modules of size
bonding states move deeper in valence band and reduces tail
30 cm × 30 cm. From our earlier study we have observed that
state density and effectively pushes up optical gap. There is
higher stabilized efficiency can be obtained using oxide based window and buffer layer. This motivates us to replace
two lone pair of electrons around oxygen atom. These lone
conventional n-a-Si:H by n-a-SiO:H to improve the performance
pair of electrons will have repulsion between them. It will
of the solar module. The use of this material in a single junction
result in antibonding splitting to widen up further from
a-Si structure enhances the short circuit current of the module
bonding states. Thus bonding and antibonding splitting will
and the conventional efficiency as well. The bandgap of n-a-
increase in silicon oxide alloy materials and optical gap of it
SiO:H film is much higher and optical absorption is less than that
will increase due to alloying with oxygen. However,
of n-a-Si:H film having the conductivity same. Due to low
depending on the deposition parameters, incorporation of O
absorption and wide optical gap of n-oxide layer allows more
into the a-Si:H network, above a certain level, results in a
fraction of light to enter into the cell after reflection from back
sharp deterioration in electronic properties and restricts its
reflector resulting in increase in short circuit current. The initial
further improvement [10]. Incorporation of O into a-Si:H
module parameters are η = 8.3%, FF = 0.69, Voc = 22.1 V and Isc = 426 mA. Module size is 30 cm × 30 cm. Out of it 10 mm is
changes the network from a dense homogeneous to a sparse
removed all around to protect from environmental degradation
inhomogeneous and strained one [13]. This phenomenon is
so the aperture area is 784 cm2. After degradation the stabilized
common to any alloy material [14]. However, in a-SiO:H the
efficiency becomes 7.2%, FF = 0.62, Voc = 22.0V and Isc = 413.8
contrast is in the nature of inhomogeneity [15]. There is
speculation that Si-rich and O-rich regions of two distinct
phases are grown at moderately high level of O-incorporation
and their nature of contribution to the optical and the electrical
In order to increase the stabilized efficiency of a single
junction amorphous solar cell researchers made different
These superior properties of a-SiO:H film encouraged us to
approaches such as incorporation of nano-crystallites in the
develop a-SiO:H films for p,n and buffer layer. In this paper
intrinsic a-Si:H films [1], improvement of window, buffer and
we have reported the preliminary results relating to the
bottom n-layer quality etc. [2-8]. Quality and thickness of the
lowering of LID in single junction amorphous mini module
window layers have great importance on improvement of the
using oxide based window, buffer and n-layers.
shorter wavelength quantum efficiency and on the carrier’s
injection [9]. In order to improve the overall efficiency of
solar cells betterment of the individual layers i.e window and
intrinsic layer property is important. Apart from that the p/i
Prepare your paper in full-size format, on US letter paper 8
interface region is also important for reducing bandgap
½ by 11 inches). For A4 paper, use the A4 settings.
mismatch and thus reducing recombination of charge carriers.
Type Sizes and Typefaces: Follow the type sizes specified in
In the interface region the recombination centre or trap centre
Table I. As an aid in gauging type size, 1 point is about 0.35
arises from internal electric field distribution due to localized
mm. The size of the lowercase letter ‘j’ will give the point
states. Wide gap bottom layer allows more light to reflect back
size. Times New Roman is the preferred font.
from the back reflector within the absorber layer. The
1) US Letter Margins: top = 0.75 inches, bottom = 1 inch,
objective of the work is to study the influence of oxide based
side = 0.625 inches. Each column measures 3.5 inches wide,
window and buffer layer on the light induced degradation
with a 0.25-inch measurement between the columns.
(LID) of a single junction a-Si solar cell. Now-a-days
2) A4 Margins: top = 19 mm, bottom = 43 mm, side = 13
researchers found that hydrogenated amorphous silicon oxide
mm. The A4 column width is 88 mm (3.45 in). The space
SCHOOL OF ELECTRONICS ENGINEERING KIIT UNIVERSITY, BHUBANESWAR, 19th - 21st December 2012
INTERNATIONAL CONFERENCE ON SOLAR ENERGY PHOTOVOLTAIC (ICSEP – 2012) A- SILICON PV: S-2 between the two columns is 4 mm (0.17 mm). Paragraph
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ACKNOWLEDGMENT and REFERENCES, and begin Subheadings
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SCHOOL OF ELECTRONICS ENGINEERING KIIT UNIVERSITY, BHUBANESWAR, 19th - 21st December 2012
INTERNATIONAL CONFERENCE ON SOLAR ENERGY PHOTOVOLTAIC (ICSEP – 2012) A- SILICON PV: S-2
[6] Karg F H et al. 1998 ‘Investigation of variously composed P/ I junction in
Amorphous Silicon Solar Cells by Time of Flight and Spectral Response
Use either SI (MKS) or CGS as primary units. (SI units are
Measurements’, Conference record of the 20th IEEE, pp. 149 [7] Zhu H and Fonash S J 1996 “Study of buffer layer design in single
encouraged.) English units may be used as secondary units (in
junction solar cells”, 25th PVSC, IEEE p 1097
parentheses). An exception would be the use of English units
[8] Chandan Banerjee, Arindam Sarker and A. K. Barua Development of wide
as identifiers in trade, such as “3.5-inch disk drive.”
band gap n-a-SiO:H films using RF-PECVD method for application in a-Si
Avoid combining SI and CGS units, such as current in
solar cell fabrication:: Ind. J. Phys. 76A (2002) 235 [9] Ding K, Aeberhard U, Finger F and Rau U 2012 Silicon heterojunction
amperes and magnetic field in oersteds. This often leads to
solar cell with amorphous silicon oxide buffer and microcrystalline silicon
confusion because equations do not balance dimensionally. If
oxide contact layers Physica Status Solidi-Rapid Research Lett.6 193 -195
you must use mixed units, clearly state the units for each
[10] Fujikake S, Ohta H, Sano A, Ichikawa Y and Sakai H 1992 High quality
a-SiO:H films and their application to a-Si solar cells Mater. Res. Soc. Symp. Proc. 258 875
[11] Sichanugrist P, Sasaki T, Asano A, Ichikawa Y and Sakai H 1994
Amorphous silicon oxide and its application to metal/n-i-p/ITO type a-Si solar
cells Sol. Energy Mater. Sol. Cell 34 415
The word “data” is plural, not singular. The subscript for the
[12] Sarker A and Barua A K 2002 Development of High Quality P-Type
Hydrogenated Amorphous Silicon Oxide Film and Its Use in Improving the
Performance of Single Junction Amorphous Silicon Solar Cells Jpn. J. Appl.
American English, periods and commas are within the
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[13] A. Morimoto, H. Noriyama and T. Shimuzu: Jpn. J. Appl. Phys., 26
at the end of a sentence is punctuated outside of the closing
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[14] A. H. Mahan, R. Robinsson and R. Tsu: Appl. Phys. Lett., 50 (1987) 335 [15] K. Haga, A. Murakami, K. Yamamoto, M. Kumano and H. Watanabe:
within the parentheses.) A graph with a graph is an “inset,”
not an “insert.” The word alternatively is preferred to the
[16] Watanabe H, Haga K and Lohner T 1993 Structure of high-
word “alternately” (unless you mean something that
photosensitivity silicion-oxeygen alloy films J. Non-Cryst. Sol. 164-166 1085
alternates). Do not use the word “essentially” to mean
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The preferred spelling of the word “acknowledgment” in America is without an “e” after the “g.” Try to avoid the stilted expression, “One of us (R. B. G.) thanks …” Instead, try “R.B.G. thanks …” Put sponsor acknowledgments in the unnumbered footnotes on the first page.
[1] Raniero L, Pereira L, Zhang S, Ferreira I, Aguas H, Fortunable E and Martins R 2004 Characterization of the density of states of polymorphous silicon films produced at 13.56 and 27.12 MHz using CPM and SCLC techniques Journal of Non-crystalline Solids 338 206 [2] Tawada Y, Tsuge K, Kondo M, Okamoto H and Hamakawa Y 1981 a‐SiC:H/a‐Si:H heterojunction solar cell having more than 7.1% conversion efficiency Appl. Phys. Lett. 39 237 [3] Tawada Y, Tsuge K, Kondo M, Okamoto H and Hamakawa Y 1982 Properties and structure of a‐SiC:H for high‐efficiency a‐Si solar cell J. Appl. Phys. 53 5273 [4] Lim K S, Konagai M and Takahashi K 1984 A novel structure, high conversion efficiency p‐SiC/graded p‐SiC/i‐Si/n‐Si/metal substrate‐type amorphous silicon solar cell J. Appl. Phys. 56 538 [5] Sakai H, Yoshida T, Fujikake S, Hama T and Ichikawa Y 1990 Effect of p/i interface layer on dark J‐V characteristics and Voc in p‐i‐na‐Si solar cells J. Appl. Phys. 67 3494
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