Atominstitut der Österreichischen Universitäten
Atomic Institute of the Austrian Universities
Publications and Conference contributions
V. Schlosser , M. Dineva , W. Markowitsch , G. Klinger
, P. Bajons , R. Ebner , J. Summhammer
Optische Bestimmung von lokalen
Schwankungen der Ladungsträgerdichte in multikristallinen Siliziumsolarzellen
Presented at Spring Meeting of German Physical Society,
Dresden, March 2003, as poster contribution HL14.95
ABSTRACT:
Bei der Herstellung von Solarzellen aus multikristallinem Silizium
(mc-Si) ist die Kenntnis der lokalen Verteilung freier Ladungsträger
sowohl während der Produktion als auch nach der Fertigstellung von
großem Interesse. Da die Messungen rasch und berührungsfrei
ablaufen sollen bieten sich optischeVerfahren an. In dieserArbeit wurde
die lokale, durch Dotierung oder Lichtanregung festgelegte, Ladungsträgerverteilung
an der Oberfläche der multikristallinen Scheiben und Zellen aus Messungen
der Plasmareflexion ermittelt. Verschiedene experimentelle Verfahren wurden
miteinander verglichen.
Full poster (PDF: 1 page, 1.1
MB)
Rita Ebner, Michael Radike, Viktor Schlosser and Johann
Summhammer
Metal Fingers on Grain Boundaries
in Multicrystalline Silicon Solar Cells
Prog. Photovolt: Res. Appl. 2003; 10: 1–13
ABSTRACT:
We have developed a method of applying a net-like finger grid to the
front of multicrystalline (mc) silicon solar cells, which lies mainly on
the grain boundaries (grain boundary-oriented-finger GBOF grid). This net
has no busbars. It is drawn by a plotter, using screen printing paste dispensed
through a fine tube. The power output of cells contacted in this manner
has been tested in a statistical study of pairs and triplets of cells of
size 100x100mm² (Bayer) and 103x103mm² (Eurosolare). In the pairs
study, pairs of neighbouring wafers of the original ingot were processed
into solar cells. One wafer received a GBOF grid, the other got the same
grid rotated by 90°, and so had little coverage of grain boundaries.
In the study of triplets the third wafer of each triplet was equipped with
a standard H-pattern of the same shading as the GBOF grid. In the pairs
study, we find that under approximately standard conditions there is an
89% chance that the GBOF grid increases power output over cells with an
identical, but 90° rotated, grid, the most probable increase being
2.6%. The triplets study shows that there is an 87% chance that the GBOF
grid increases power output over cells with the standard H-pattern, the
most probable increase being 2.5%.
Full paper (PDF: 19 pages, 4
Tables, 5 Figures, 399k)
V. Schlosser, W. Markowitsch, G. Klinger, P. Bajons,
S. Chancy, R. Ebner, J. Summhammer
Electro-Optical Properties of Multicrystalline
Silicon during Solar Cell Processing
Presented at Conference "PV in Europe", Rome, Oct. 7-11,
2002 (Proceedings paper OA2.2)
ABSTRACT:
We used different experimental setups to detect the optical reflection
of free carriers in initial and partly processed multicrystalline silicon
wafers. With these contactless and 'preparation-free' characterization
tools we monitored the spatially resolved diffusion length of photoexcited
carriers at each step of the solar cell's preparation cycle. A significant
change in the distribution of defects was observed. The results are used
to (i) improve the steps of solar cell preparation and (ii) to predict
an optimized layout of the front metal grid for each cell depending on
its individual defect distribution.
Full paper (PDF: 4 pages; 6 pictures)
Rita Ebner, Maria Raith, Viktor Schlosser and Johann
Summhammer
Galvanic Grain Boundary Contacts
on Multicrystalline Silicon Solar Cells
Presented at Conference "PV in Europe", Rome, Oct. 7-11,
2002 (Proceedings paper OD2.4)
ABSTRACT:
We present new results of putting the metallic front contact pattern
of multicrystalline silicon solar cells over and along grain boundaries
(Grain Boundary Oriented Finger grid – GBOF-grid). In a previous study
the contacts were formed by automated grain boundary detection and writing
of the contact pattern with ordinary screen printing paste. Now we used
a galvanic method with nickel as a diffusion barrier and silver as the
conductor, in view of a possible application in laser grooved buried contact
cells. This gave very low contact and series resistances. Using Baysix®
100x100-wafers, we compared so called ON-cells, which received the GBOF-grid
so that the front contacts ran mostly along grain boundaries, OFF-cells,
where the same pattern was used but was rotated by 90° to give only
little coverage of grain boundaries, STD-cells with the H-pattern of most
commercial silicon solar cells, and GRD-cells with a geometric rectangular
grid pattern. With the same total shading on all four kinds of patterns,
a clear advantage for the grain boundary contacted ON-cells is found, exceeding
the results of the previous study. Under approximately standard conditions,
ON-cells gave at least 5% more power than the STD-cells and in some batches
over 10% more. Their performance improvement over the OFF- and the GRD-cells
shows similar values.
Full paper (PDF: 4 pages; 1 table,
5 pictures)
Rita Ebner, Michael Radike, Viktor Schlosser and Johann
Summhammer
Metal Fingers on Grain Boundaries
in Multicrystalline Silicon Solar Cells
Presented at 17th European Photovoltaic Solar Energy
Conference, Munich, Oct. 22-26, 2001 (Proceedings, Volume I, paper OC9.1,
p.80-83; WIP, Munich 2002)
ABSTRACT:
We have developed a method of applying a net-like finger grid to the
front side of multicrystalline (mc) silicon solar cells, which lies mainly
on the grain boundaries (Grain Boundary Oriented Finger grid, GBOF grid).
This net has no busbars. It is drawn by a plotter using screen printing
paste.
The efficiency of cells contacted in this manner has been tested in
a comparative study of pairs and triplets of cells of size 100x100mm2 (Bayer)
and 103x103mm2 (Eurosolare). In the pairs-study pairs of neighbouring wafers
of the original ingot were processed into solar cells. One wafer received
a GBOF-grid, the other got the same grid rotated by 90 degrees and so had
little coverage of grain boundaries. In the triplets study a third neighbouring
wafer was added and equipped with a standard H-pattern of the same shading
as the GBOF-grid. Many pairs and triplets were made. The pairs study showed
that the GBOF-grid gives solar cells with 3.7% more output, on average,
under approximately standard conditions. The triplets study shows that
the GBOF-grid increases power output by 2.5%, on average, over the standard
H-pattern.
Full paper (PDF: 4 pages)
V. Schlosser, R. Ebner, W. Markowitsch, P. Bajons, G.
Klinger, A.A. El-Amin, J. Summhammer
Investigation of Evaporated Front
Contacts along the Grain Boundaries of Multicrystalline Silicon Solar Cells
Presented at 17th European Photovoltaic Solar Energy
Conference, Munich, Oct. 22-26, 2001 (Proceedings, Volume II, paper VC1.17,
p.1472-1475; WIP, Munich 2002)
ABSTRACT:
A series of sets of multicrystalline silicon solar cells have been
prepared. One cell of each set was equipped with a front contact grid along
the grain boundaries. A second cell was equipped with the same grid but
rotated by 90 degrees and onto the third cell a geometrical standard grid
was applied. The grids were either
prepared by plotting silver ink lines and subsequent burn in or by
photolithographically structured Ni/Ag layers deposited by evaporation
or a galvanic process. No passivation or protection against reflection
losses were applied. A statistical evaluation of the solar cell parameters
for two illumination intensities in a temperature range between 295 K and
330 K was done. At room temperature the gain of maximum output power for
cells with the grid on the grain boundaries for high and low light intensities
was 1.17 and 1.15, respectively, compared with cells having a standard
grid. The average linear temperature coefficient for the power output was
determined to be -0.80 %K-1 for cells with a grain boundary grid and -0.74
%K-1 for cells with a standard grid. For one cell prepared by the photolithographic
method a maximum power output of more than 10 mWcm-2 was observed under
1 kWm-2 irradiation at ambient temperature.
Full paper (PDF: 4 pages)
M.Radike, J.Summhammer Novel process of grain boundary
metallisation on mc Si Solar cells
Solar Energy Materials & Solar Cells 65 (2001) 303-309
Abstract:
The electronic properties of multicrystalline silicon are heavily influenced
by impurities concentrated along grain boundaries that increase the recombination.
Dopants diffuse preferentially down the grain boundaries, which leads to
a low resistance path between n and p sections. These effects decrease
the efficiency of multicrystalline silicon solar cells. Additionally, the
efficiency is lowered due to the shading of the front grid metallisation
lines. We present a new way to combine the grain boundaries and the front
grid metallisation to improve the efficiency of multicrystalline silicon
solar cells. A first approach has been developed to produce multicrystalline
silicon solar cells with a front contact metallisation following the grain
boundaries: The different grain boundaries of a wafer are detected by optical
scanning. Together with the emitter sheet resistivity this image serves
as an input to calculate a grid of finger lines that follow the grain boundaries
wherever possible. Onto these detected grain boundaries the metallisation
is performed by evaporative deposition of copper and photolithography.
We report on the successful implementation of such a grid on 100x100mm²
wafers.
M. Radike and J.
Summhammer Electrical and Shading Power Losses
of Decorative PV Front Contact Patterns
Progress in Photovoltaics: Research
and Applications 7 (1999) 399-407
M.Radike , J.
Summhammer , V. Schlosser
and A. Breymesser
Optimization of artistic contact
patterns on multicrystalline silicon solar cells
Proceedings of 2nd World Conference on Photovoltaic Solar
Energy Conversion, Vienna, Austria, July 1998
Abstract:
The acceptance of photovoltaic modules in highly visible places like
walls and roofs of buildings, or for small scale village use, is in a large
part determined by non technical aspects, most of all by the visual appeal.
The design of the surfaces of cells and modules must therefore meet two
optimization criteria: High energetic output and attractive appearance.
As the bus bars of the front collection grid are often considered visually
annoying, we have tried to convert them into an asset by incorporating
artistic shapes into them. Ten different designs have been analysed and
screen printed onto 103 x 103 mm2 multicrystalline Si solar
cells. For a 15 % efficient cell with standard H-pattern we have found
that it would at worst be reduced to an efficiency of 14.5 % when equipped
with one of our artistic bus bar designs.
Online Version (in English) including
16 pictures (JPG format)
12th European Photovoltaic Solar Energy Conference; Amsterdam,
The Netherlands, April 1994
"Investigations of a novel front contact grid on poly silicon solar cells"
Using poly silicon wafers as starting material 3 cm x 3 cm solar cells
were made. Pairs of solar cell devices were processed simultaneously using
sets of subsequent wafers which exhibit essentially the same grain structure.
The front metallisation of the reference cell was done by painting a conventional
grid structure with silver ink whereas onto the other cell the metal structure
was painted along the grain boundaries. Current- voltage measurements
on a series of cell pairs were made in the dark and under illumination.
Diode parameters - recombination current, j01, diffusion current,
j02, shunt conductance, GSH , and series resistance,
RS as well as solar cell parameters short circuit current, iSC,
open circuit voltage, VOC , and curve fill factor, CFF, were
determined. The comparison of the statistically evaluated results shows,
that the series resistance of the reference cells is more than 20 per cent
larger than the one found for the cells which have a front contact grid
along the grain boundaries, resulting in an average increase of the curve
fill factor of more than 5 per cent. Furthermore the individual results
of these two parameters as well as of the load resistance at conditions
of maximal power output differ considerably less from the mean value for
these cells compared to the values of the reference devices.
Online Version in English including
2 pictures (JPG format)
Other Publications
11th Workshop an Quantum Solar Energy Conversion; Wildhaus,
Switzerland, March 1999
M. Radike and J.
Summhammer
"Design and characterisation of novel front contact
patterns on multicrystalline silicon solar cells"
The visual appeal is an important criterion for the acceptance of photovoltaic
modules in facades and roofs or buildings, or in village electrification.
Therefore, on the one
hand, we design artistic front contact patterns converting the busbars
into an attractive feature without an undue decrease of efficiency. Such
designs can be applied on
mono- as well as on multicrystalline silicon wafers. We show that our
recently designed patterns lead to lower efficiency, due to increasing
resistivity and shading losses,
of only about 0.7% absolute compared to the standard pattern under
1-sun conditions. On the other hand we develop a method based on pattern
recognition to apply the
finger grid on the front side along the grain boundaries of the multicrystalline
silicon. This will increase the area of high-efficiency inner grain regions
and reduce series
resistance losses at the grain boundaries. Therefore an overall increase
of efficiency can be expected.
49th Conference of the Austrian Physics Society; Graz,
Austria, September 1998
"Optimization of artistic contact patterns on multicrystalline silicon
solar cells"
The acceptance of photovoltaic modules in highly visible places like walls
and roofs of buildings, or for small scale village use, is in a large part
determined by non technical aspects, most of all by the visual appeal.
The design of the surfaces of cells and modules must therefore meet two
optimization criteria: High energetic output and attractive appearance.
As the bus bars of the front collection grid are often considered visually
annoying, we have tried to convert them into an asset by incorporating
artistic shapes into them. Ten different designs have been analysed and
screen printed onto 103 x 103 mm2 multicrystalline Si solar
cells. For a 15 % efficient cell with standard H-pattern we have found
that it would at worst be reduced to an efficiency of 14.5 % when equipped
with one of our artistic bus bar designs.
HERAEUS - Semiconductor course; TU COTTBUS, Germany, September 1997:
"Novel front contact patterns on polycrystalline silicon solar cells"
To increase the efficiency of multicrystalline silicon solar cells the
metal contact on the front side of the wafer is not designed as a geometrical
grid as in most cases industrially done but painted on the boundaries of
the silicon grains. On the one hand this increases the short circuit current,
ISC, avoiding an additional shading of the active grain area. On the other
hand it decreases the series resistance RS. Until now the only way to get
different visual impressions of solar cells was to change the colour by
varying the thickness of the anti reflex coating (ARC). Now we try to convert
the (necessary) bus bars from a visually annoying part into an asset by
incorporating artistic shapes into them. The aim is to do that without
an excessive increase of losses and therefore an decrease of efficiency.
This should lead to a larger field for the use of multicrystalline silicon
solar cells (for example in facades, on roofs, ...)
Media Presence
PHOTON
The International Photovoltaic Magazine
Issue 5-99, pages 27-28, by J.
Summhammer and M. Radike
Report on busbar design at the
Atominstitute of the Austrian Universities (AIAU)
at the BIMODE meeting, Cologne,
Germany, June 1999.
PHOTON
The International Photovoltaic Magazine
Issue 5-99, pages 26-28, by Anne
Kreutzmann BIMODE modules debut amid skepticism
and enthusiasm:
Architects and industry evaluate
BIMODE work group progress
PHOTON
The International Photovoltaic Magazine
Issue 3-99, pages 30-31, by Anne
Kreutzmann The Rolls Royce of Photovoltaics:
EU project for aesthetic solar
modules introduces first designs
PHOTON das Solarstrom-Magazin
Ausgabe 5-99, Seite 46-48, by Anne
Kreutzmann Zwischen Skepsis und Begeisterung:
BIMODE-Module werden Architekten
vorgestellt
Available only in German
Scientific supplement "SPECTRUM" of 31 October 1998, by T.
Kramar
"Form and function: Silver brilliance and efficiency of solar cells"
"Crystal" and "BIMODE" are two solar energy projects with two Austrian
expert teams involved. They are working in basic research as well as in
applied research fields ...
Online VersionGERMAN ONLY! (with
kind permission of "PRESSE-Online") including 5 pictures (JPG format)
