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High-productive aluminum deposition of back contacts for hetero-junction solar cells by electron beam evaporation

: Heinß, Jens-Peter; Schlemm, Hermann; Wünsch, Frank


European Commission:
32nd European Photovoltaic Solar Energy Conference and Exhibition, EU PVSEC 2016 : 20 - 24 June 2016, Munich, Germany
Munich, 2016
ISBN: 3-936338-41-8
European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC) <32, 2016, Munich>
Conference Paper
Fraunhofer FEP ()
back contact; metallization; cost reduction; high deposition rate

Currently back contacts of Silicon HJT (Hetero Junction Technology) cells are sputtered or screen printed Ag-layers or structures. The present work aims to replace these cost-intensive manufacturing steps by electron beam evaporation of aluminum using axial beam guns. Al-layers of the necessary thickness have been evaporated with a dynamic deposition rate of up to 3000 nm.m/min while keeping the solar cell below 200°C to avoid any thermal damage of underlying layers and junctions. The deposited aluminum layers exhibit specific electrical resistance of 2.8.10-6 Ω.cm, specific electrical contact resistance of 10-3 Ω.cm2 and more than 92 % averaged reflection in the NIR. By exchanging only the metallization step in a standard HJT cell processing without further process-optimization lead to cell efficiencies of 20.6 %.It can be stated that the electron beam evaporation can meet the technical and economical demands of the HJT production process. The high deposition rate can ensure the rear-side metallization of a 100 MW production line in one single deposition equipment.