Investigations of laser and design parameters of via holes on mechanical strength of metal wrap through solar cells

In photovoltaic industry cell concepts with rear side contacts, such as the metal wrap through solar cell design, have been developed to decrease the module manufacturing costs. In the metal wrap through solar cells, holes are introduced at the beginning of cell manufacturing. These holes could influence the strength and the breakage rate of wafers and cells. In this work, full size monocrystalline silicon wafers with different number and orientation of holes were investigated in 4-point bending tests regarding the strength behavior. Furthermore, small monocrystalline silicon samples with one central hole, drilled with different laser parameters, were analyzed in ring-on-ring tests. As a result, there is only small influence of holes on the strength on wafer level. Though, the investigation of small chips showed that different laser parameters can change the strength of the material in the region of the holes.