Optimizing the front side metallization process using the Corescan

In solar cell manufacturing it is difficult to optimize screen printed front side metallization, in particular to obtain good contact over the entire cell. The Corescan enables mapping of contact resistance of full cell surfaces. Using these mappings, it is possible to diagnose and exclude reasons for poor contact formation. In this study, several process conditions have been studied. Cross-belt temperature non-uniformity in the firing furnace turns out to be a reason for large contact resistance differences. This shows that the acceptable firing temperature range can be considerably increased if a constant temperature profile across the belt width is realized. Further, it is shown that plasma etching for isolation gives cause for an increase of the contact resistance of the fingers at the cell edges. Finally, contact resistance differences related to emitter non-uniformity are found. To summarize, the Corescan is a powerful tool that enables easy optimization of front side metallization.