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Title:
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Explanation of high solar cell diode factors by non-uniform contact resistance
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Author(s):
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Published by:
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Publication date:
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ECN
Solar Energy
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1-4-2004
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ECN report number:
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Document type:
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ECN-RX--04-009
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Article (scientific)
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Number of pages:
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16
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Published in: Progress in Photovoltaics: Research and Applications (John Wiley & Sons Ltd.), , 2005, Vol.13, p.3-16.
Abstract:
The current density-voltage (J-V) curve that characterises
the performance of a solar cell is often rounded, resulting in reduced
efficiency. When fitting to the standard one dimensional models, it
is often found that the rounding cannot be fitted by the series resistance
only. In these cases, the diode factor m or the depletion region saturation
current density J0DR (depending on the model used) is increased.
This behaviour could not be explained so far; this paper discusses if
a non-uniform contact resistance of the front side metallisation leads
to an increase of m or J0DR .
The theoretical part of the investigation is the simulation
of the curve for a cell with two regions with different contact resistance.
It was found indeed that m or J0DR is increased, while the
series resistance is not increased as much as expected.
The experimental part was the calculation of the J-V
curve of a high m solar cell using local contact resistances measured
with the so-called Corescan and the cell?s resistanceless J-V curve
as measured with the so-called Suns-Voc method. The calculated
curve approximated the actual curve quite well, demonstrating in practice
that high diode factors can be explained by non-uniform contact resistance.
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