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Atmospheric pressure plasmas for crystalline silicon photovoltaics

Atmosphärendruck-Plasma für kristalline Silicium-Photovoltaikbauelemente
: Hopfe, V.; Sheel, D.W.; Möller, R.

Society of Vacuum Coaters -SVC-, Albuquerque/NM:
Society of Vacuum Coaters. 51st Annual Technical Conference 2008. Proceedings : April 19 - 24, 2008, Chicago, IL, USA
Albuquerque: SVC, 2008
Society of Vacuum Coaters (Annual Technical Conference) <51, 2008, Chicago/Ill.>
Conference Paper
Fraunhofer IWS ()
Atmosphärendruck; photovoltaische Zelle; Plasmabeschichten; Silicium

Plasma processing at atmospheric pressure (APP) has attractions for both economic and technological reasons. Potential cost saving factors are associated with on-line processing capability, which substantially reduces substrate handling cost, and increased throughput due to high rates. Capital cost savings for both equipment and line space (foot print), and relative ease of integration, are further benefits in comparison to low pressure technology approaches. These economic and technical benefits are of key interest for next generation mass production of crystalline silicon photovoltaic power cells. Potential application areas comprise both AP-PECVD and plasma chemical ('dry') etching. Targeting at technologies being compatible with industrial requirements in pholovoltaics three key challenging aspects will be addressed: availability of scalable wide area plasma sources having sufficient 'robustness' for long-term continuous operation, plasma reactors being applicable for continuous air-to-air processing, and processing rates being compatible with the throughput requirements of the whole production line. In this contribution we will describe both thermal (microwave, DC ArcJet) and non thennal (glow discharge DBD) APP approaches. The described AP-Plasma reactors have been designed for continuous processing with (dynamic) rates for PECVD of up to 2 nm-m/s and for plasmachemical etching up to 60 nm-m/s. Both plasma chemical etching and plasma coating have been explored for introducing into crystalline silicon photovoltaics. Nano textures with reflectivity in the visible range down to 1% have been achieved by plasma chemical etching. Carrier lifetime is increased by silicon nitride coating to a level being compatible with state-of-the-art low pressure PECVD coatings.