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Long-term and annealing stable, solderable PVD metallization with optimized Al diffusion barrier

: Kumm, J.; Chacko, R.V.; Samadi, H.; Hartmann, P.; Eberlein, D.; Jäger, U.; Wolf, A.

Fulltext urn:nbn:de:0011-n-3668471 (492 KByte PDF)
MD5 Fingerprint: e18d71ee50102e24b1562a9aae22df1b
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Created on: 25.11.2015

Energy Procedia 77 (2015), pp.374-381
ISSN: 1876-6102
International Conference on Crystalline Silicon Photovoltaics (SiliconPV) <5, 2015, Constance>
Journal Article, Conference Paper, Electronic Publication
Fraunhofer ISE ()
Fraunhofer IISB ()
PV Produktionstechnologie und Qualitätssicherung; Silicium-Photovoltaik; Kontaktierung und Strukturierung; Pilotherstellung von industrienahen Solarzellen; Modulintegration; metallization; TiN; barrier; Soldering; stability

Since passivated emitter and rear cells (PERC) and other silicon solar cell concepts with evaporated aluminum (Al) as rear metallization are incompatible with a common solder process, in this work an annealing stable,solderable and long-term stable metallization scheme deposited by physical vapor deposition (PVD) is developed. The solder stack that complements the Al metallization consists of sputter deposited TiN/Ti/Ag or TiN/NiV/Ag, whereby the TiN layer serves as a diffusion barrier against Al. It is therefore optimized by varying sputter parameters and by stuffing the grain boundaries with oxygen. On the optimized stack a cell-interconnector can be conventionally soldered even after a strong annealing step of 15 min at 425 °C, which sets this concept apart from other PVD metallization approaches. Cell efficiency is not influenced by the solder stack compared to a reference rear metallization by plain evaporated Al. Additionally, long-term stability of the solder-joints on the metallization schemeis investigated by thermal aging of solder-joints and thermal cycling of demo moduleswith PERC cells.