Etching of PVD metal layers for contact separation of back contact silicon solar cells using inkjet-printing

Back contact solar cell concepts feature both metal contact polarities on the rear side of the wafer. PVD (Physical Vapor Deposition) is one option for high quality metal layers. To create a working device the metal contacts must be separated. This work reports on the evaluation of an economic process route using an etching ink that is inkjet-printed onto metal layers. Drop on demand inkjet technology is very well suited for the deposition of such etchants onto the thin wafers as it allows for the well-defined deposition of complex structures needed e.g. for the rear side of back-contact solar cells. It is investigated how the amount of ink and thus reactive species influences the width of the etched structures and if they are electrically isolated. The width of the etched structures has been reduced down to 65 mm on 1000 nm thick Al-layers by adjusting the amount of ink printed on the metal layers. The separation was demonstrated by measuring the electrical resistance between the separated metal areas. The presented process provides a structuring solution for the cost effective contact separation for back contact solar cells. The feasibility has been shown by printing a meander structure which is the typical contact separation layout for a BC-BJ (Back-Bontact Back-Junction) solar cell.