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Title:
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Bulk and surface passivation of silicon solar cells accomplished by silicon nitride deposited on industrial scale by microwave PECVD
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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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1-10-2005
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ECN report number:
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Document type:
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ECN-RX--05-036
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Article (scientific)
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Number of pages:
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19
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Published in: Progress in Photovoltaics: Research and Applications (John Wiley & Sons Ltd.), , 2005, Vol.13, p.551-569.
Abstract:
Bulk and surface passivation by silicon nitride has become an indispensable
element in industrial production of multicrystalline silicon (mc-Si)
solar cells. Microwave PECVD is a very effective method for high-throughput
deposition of silicon nitride layers with the required properties for
bulk and surface passivation. In this paper an analysis is presented
of the relation between deposition parameters of microwave PECVD and
material properties of silicon nitride. By tuning the process conditions
(substrate temperature, gas .ows, working pressure) we have been able
to fabricate silicon nitride layers which ful.ll almost ideally the
four major requirements for mc-Si solar cells: (1) good anti-re.ection
coating (refractive index tunable between 2.
0 and 2.3); (2) good surface passivation on p-type FZ wafers (Seff<30
cm/s); (3) good bulk passivation (improvement of IQE at 1000 nm by 30%
after short thermal anneal); (4) long-term stability (no observable
degradation after several years of exposure to sunlight). By implementing
this silicon nitride deposition in an inline production process of mc-Si
solar cells we have been able to produce cells with an efficiency of
16,5%. Finally,
we established that the continuous deposition process could be maintained
for at least 20 h without interruption for maintenance. On this timescale
we did not observe any signi.cant changes in layer properties or cell
properties. This shows the robustness of microwave PECVD for industrial
production.
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