"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.
Online
Version (in English) (Link zur European Society for Quantum Solar Energy
Conversion)
Die PRESSE: Scientific supplement
"SPECTRUM" from 31 October 1998 written 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 are involved. They are working in basic research as well as
in applied research fields ...
Online VersionGERMAN ONLY! (with kind
permission of "PRESSE-Online", the Copyright keeper) including 5 pictures
(JPG format)
2nd World Conference on Photovoltaic Solar Energy Conversion; Vienna, Austria,
July 1998
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.
Online Version (in English) including 16 pictures
(JPG format)
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, ...)
Online Version: not yet available
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)
PHOTON - INTERNATIONAL
PHOTON - GERMANY
Die PRESSE: Scientific supplement
"SPECTRUM" from 31 October 1998 written by T.
Kramar