Continuous wave laser processing for electrical and mechanical stable solar cells with Ni-Cu metallization

Two process sequences for the fabrication of Ni-Cu plated solar cells with a selective emitter by means of laser processing are presented. The purpose of the highly doped deep emitter is in this case not only to lower the contact resistance but to prevent shunting by nickel silicide which grows into the wafer. This silicide formation is found to be a key step in creating excellent contact adhesion. SEM imaging has been used to characterize the coverage of contact openings with nickel silicide. Electrical and mechanical properties of the fabricated solar cells as well as the advantages and disadvantages of the presented process sequences are discussed using SunsVoc and peel force measurements.