Solder Interconnection of Aluminum Foil Rear Side Metallization for Passivated Emitter and Rear Solar Cells

9 Pages Posted: 4 Apr 2018 Last revised: 20 Apr 2018

See all articles by Angela De Rose

Angela De Rose

Fraunhofer Institute for Solar Energy Systems (ISE)

Achim Kraft

Fraunhofer Institute for Solar Energy Systems (ISE)

Sophie Gledhill

Fraunhofer Institute for Solar Energy Systems (ISE)

Muhammad Tahir Ali

Fraunhofer Institute for Solar Energy Systems (ISE)

Thomas Kroyer

Fraunhofer Institute for Solar Energy Systems (ISE)

Claudia Pscherer

SCHLENK Metal Foils GmbH & Co. KG

Martin Graf

Fraunhofer Institute for Solar Energy Systems (ISE)

Jan Nekarda

Fraunhofer Institute for Solar Energy Systems (ISE)

Ulrich Eitner

Fraunhofer Institute for Solar Energy Systems (ISE)

Date Written: April 15, 2018

Abstract

Foil metallized (FolMet) solar cells combine the high-efficiency PERC technology and a cost-efficient rear side metallization based on a 9 µm thin aluminum foil. Laser fired contacts are used to attach the foil to the rear side and allow for the mechanical and electrical contact to the cell. Direct soldering on aluminum is hampered by a native oxide film formed immediately when exposed to air. To realize the cell interconnection by a standard solder process the Al foil is coated by sputter deposition or roll cladding of solderable layers. This work evaluates the solderability of 200 µm thick coated Al foils with the common solder interconnection process established in photovoltaics using standard copper ribbons for module integration. Our analysis reveals for both coating approaches strong initial mechanical adhesion of > 4 N/mm after soldering and very low contact resistivities of < 1.6 µ∙cm2. The contact resistivity shows no degradation after isothermal aging within 1000 hours at 85 °C. The mechanical adhesion of the sputter coated Al foils remains at 3 N/mm under thermal aging of more than 1000 h at 85 °C whereas the adhesion for the Al foils coated by roll cladding drops strongly to values of < 1 N/mm already after 50 hours. SEM images indicate that this effect is caused by re-oxidation of the aluminum surface supported by micro cracks in the solderable top layer.

Keywords: Interconnection, Soldering, Aluminum Foil, PERC, Sputter Deposition, Roll Cladding

Suggested Citation

De Rose, Angela and Kraft, Achim and Gledhill, Sophie and Ali, Muhammad Tahir and Kroyer, Thomas and Pscherer, Claudia and Graf, Martin and Nekarda, Jan and Eitner, Ulrich, Solder Interconnection of Aluminum Foil Rear Side Metallization for Passivated Emitter and Rear Solar Cells (April 15, 2018). 7th Workshop on Metallization and Interconnection for Crystalline Silicon Solar Cells, 2017. Available at SSRN: https://ssrn.com/abstract=3152428 or http://dx.doi.org/10.2139/ssrn.3152428

Angela De Rose (Contact Author)

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Achim Kraft

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Sophie Gledhill

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Muhammad Tahir Ali

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Thomas Kroyer

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Claudia Pscherer

SCHLENK Metal Foils GmbH & Co. KG ( email )

Barnsdorfer Hauptstraße 5
Roth, 91154
Germany

Martin Graf

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Jan Nekarda

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

Ulrich Eitner

Fraunhofer Institute for Solar Energy Systems (ISE) ( email )

Heidenhofstrasse 2
Freiburg, DE 79110
Germany

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