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Development of silicon heterojunction metal wrap through solar cells

 
: Dirnstorfer, Ingo; Schilling, Niels; Körner, Stefan; Gierth, Paul; Sontag, Detlef; Jordan, Paul M.; Simon, Daniel K.; Fengler, Franz P.G.; Mikolajick, Thomas; Linaschke, Dorit; Dani, Ines; Marcinkowski, Manja; Eberstein, Markus; Rebenklau, Lars; Partsch, Uwe

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Volltext ()

Bokhoven, T.P. ; European Commission:
29th European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2014 : Proceedings of the international conference held in Amsterdam, The Netherlands, 22 - 26 September 2014, DVD
München: WIP, 2014
ISBN: 3-936338-34-5
S.1044-1048
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <29, 2014, Amsterdam>
Englisch
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IKTS ()
Fraunhofer IWS ()

Abstract
A silicon heterojunction solar cell basing on amorphous and crystalline silicon is combined with the metal wrap through technology. In this way, the geometrical front side metallization area is reduced from about 7 % to below 5 %. The novel cell concept bases on a back junction configuration to avoid complex insulation steps within the via holes. Furthermore, well-passivated via holes are fabricated in a 532 nm laser process after the thin film depositions. As an alternative, the 1064 nm laser process is investigated, however, the result is a high surface recombination rate and a low effective carrier lifetime in the via vicinity. Scanning electron microscopy cross sections of via holes indicate a different surface oxide formation for both laser lines and this result suggests that this oxidation is crucial for the via hole passivation. Via holes in silicon heterojunction solar cells also have very high surface recombination, when the via hole formation is performed prior to wet chemical cleaning and texturing steps, which is the standard sequence in diffused emitter metal wrap through solar cells. The via metallization bases on a novel low-temperature silver paste, which is deposited by vacuum assisted screen printing. Cross sections reveal excellent via filling, which results in a low electrical resistance. The via-related specific solar cell series resistance is below 80 mΩcm2. Finally, the solderability of the rear side metallization was evaluated for later module integration.

: http://publica.fraunhofer.de/dokumente/N-328407.html