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Plasma etching at atmospheric pressure for rear emitter removal in crystalline Si solar cells

: Lopez, E.; Dani, I.; Hopfe, V.; Heintze, M.; Hauser, A.; Möller, R.; Wanka, H.

Poortmans, J. ; European Commission, Joint Research Centre -JRC-:
21st European Photovoltaic Solar Energy Conference 2006. Proceedings. CD-ROM : Proceedings of the international conference held in Dresden, Germany, 4 - 8 September 2006
München: WIP-Renewable Energies, 2006
ISBN: 3-936338-20-5
European Photovoltaic Solar Energy Conference <21, 2006, Dresden>
Conference Paper
Fraunhofer IWS ()
Abfallvermeidung; Ausbeute; Bogenentladung; Kontaktieren; Kostenreduktion; kristalliner Stoff; Nebenschlusswiderstand; Oberflächenbeschaffenheit; Passivierung; Plasmaätzen; Plasmagenerator; Silicium; Sonnenemitter; Sonnenzelle; Wafer=Halbleiterplättchen; Wirkungsgrad

In this contribution edge isolation of crystalline silicon solar cells by dry etching is described. Dry etching has the potential to replace wet chemical etching steps in solar cell processing. An innovative atmospheric pressure plasma chemical etching process is introduced and feasibility for dry etching is demonstrated. The atmospheric plasma processing is expected to lead to reduced costs because of reduced wafer breakage rate, reduced chemical waste and reduced handling operation due to in-line processing. A reactive plasma is generated in a linear extended arc jet source operating at atmospheric pressure and used to remove the rear side emitter. The wafers are continuously moved through the reactor, resulting in an in-line process which can be applied between nitride deposition and contact screen printing. Plasma enhanced chemical etching of 125 mm x 125 mm mono-crystalline silicon wafers has been carried out. Different surface morphologies have been observed such as smooth surfaces, pyramids of several micrometers or nano-textured surfaces depending on the etch gas and process conditions. Good shunt resistance values of 14 kOhm cm(exp 2) were achieved. Industrial trials result in cell efficiencies being equivalent to the wet chemical reference process.