How to Obtain Solderable Al/Ni:V/Ag Contacts

• Published in: Energy procedia Vol. 38; pp. 375 - 379
• Main Authors: Lehr, Martin, Heinemeyer, Frank, Eidelloth, Stefan, Brendemühl, Till, Kiefer, Fabian, Münster, Daniel, Lohse, Anja, Berger, Miriam, Braun, Nadja, Brendel, Rolf
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2013
• Subjects: evaporated aluminum; metallization; Silicon solar cell; Solderability; Silicon solar cell; metallization; Solderability; evaporated aluminum
• ISSN: 1876-6102; 1876-6102
• DOI: 10.1016/j.egypro.2013.07.292

We investigate process sequences for obtaining solderable Al/Ni:V/Ag contacts to PERC-type crystalline Si solar cells by in-line Al evaporation. For a high cell efficiency the evaporated aluminum must be annealed at 350°C for about 5min. We find that annealing the Al/Ni:V/Ag metallization stack at temperatures above 150°C destroys the solderability of the wetting layer. A solution for this problem is to first deposit the 2.5μm Al layer by evaporation, then anneal the cell at 350°C for 10min, and finally sputter a double layer of Ni:V/Ag with respective thickness values of 200nm and 25nm. This process leads to a contact resistivity lower than 1 mΩcm2. The solderablility is proven by a peel force greater than 3N/mm. We present a solderable PERC cell with Al/Ni:V/Ag rear side metallization and an efficiency of 18.9%.