SPLTRAK Abstract Submission
Laser-weld qualification methods for Al foil interconnection of back-contacted cells to predict module reliability
Barry B. Hartweg1,2, Kathryn C. Fisher1,2, Zhengshan J. Yu1,2, Zachary C. Holman1,2
1Arizona State University, Tempe, AZ, United States
/2SunFlex Solar, LLC, Tempe, AZ, United States

Conductive backsheet modules have been fabricated using inexpensive Al foil, where the bond between foil and cells are made using a laser-welding process.  The durability of this interconnection has been proven via thermocycling (TC) on a millisecond laser in the past.  However, this laser is too slow for large-scale manufacturing, so a faster nanosecond laser needs to be proven still.  A laser-shunted module demonstrated a durable interconnection that can pass TC, but it resulted in an upfront power loss of 34% from the laser-processing.  Microscopy demonstrated that the laser-welding ablated the Ag contact down to the Si surface, causing a shunt of the n-type contact.  Quality welds only interact with the surface of the Ag to promote adhesion without damaging the cell performance.