Development of lead-free silver ink for front contact metallization

In this paper lead-free silver ink for the front side metallization of silicon solar cells is investigated. Lead is replaced by bismuth. The etching of the silicon nitride anti-reflection coating and the crystallite formation is studied by varying the amount of bismuth oxide added to the ink. Bismuth oxide was either incorporated into the glass frit or added as a powder. The results are compared to our standard lead based standard ink. All inks were applied with aerosol jet printing. For characterization SEM imaging, contact resistance measurements, and the current–voltage-characteristics of the prepared solar cells are used. Concerning the solar cell efficiency, it is found that bismuth glass inks provide a similar efficiency in comparison to the lead based ink.

► Development of lead-free glass for silver inks printed with seed layer technique.
► SEM contact analysis showed correlation to the bismuth amount in the glass.
► Bismuth glass ink showed equal or better solar cell efficiency than lead glass ink.
► Discussion of the failure mode of solder ribbon pull tested seed layer busbars.