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Solder interconnection of aluminum foil rear side metallization for passivated emitter and rear solar cells

: Rose, Angela de; Kraft, A.; Gledhill, S.; Ali, M.T.; Kroyer, T.; Pscherer, C.; Graf, M.; Nekarda, J.; Eitner, U.

Volltext urn:nbn:de:0011-n-5040022 (809 KByte PDF)
MD5 Fingerprint: ad44d669b93befc47af686369e22a687
Erstellt am: 17.8.2018

Metallization & Interconnection Workshop 2017. Workshop Program. Online resource : 7th Workshop on Metallization & Interconnection for Crystalline Silicon Solar Cells, Konstanz, October 23 and 24, 2017
Konstanz, 2017
9 S.
Workshop on Metallization & Interconnection for Crystalline Silicon Solar Cells <7, 2017, Konstanz>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()
photovoltaisches Modul; Systeme und Zuverlässigkeit; Photovoltaik; Silicium-Photovoltaik; Photovoltaische Module und Kraftwerke; Pilotherstellung von industrienahen Solarzellen; Modultechnologie; interconnection; PERC; Soldering; foil; deposition

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 μΩ∙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 the re-oxidation of the aluminum surface supported by micro cracks in the solderable top layer.