Stress and Fracture of Crystalline Silicon Solar Cell Interconnection Using Electrically Conductive Adhesive with Composite Metal Fillers for More Reliable Next Generation PV System Design

Conventional soldered interconnects—necessarily requiring high-temperature processes to melt solder (tin)—are posing reliability challenges to crystalline silicon solar cell modules due to residual stress stemming from the mismatch of the coefficient of thermal expansion of the materials involved. On the other hand, electrically conductive adhesives (ECAs) have been shown to exhibit sufficiently promising improvements in mechanical and electrical properties to be used as silicon solar cell interconnects. However, the current ECA technology is dominated by ECAs with dispersed silver particles, which makes them costly and could cause embrittlement of the ECA at higher concentrations. This study investigates the potential application of a novel ECA, with composite metal particles, made of a nickel and Sn95Ag4Cu1 solder mixture and dispersed in a high-density polyethylene matrix for the solar cell interconnection. The test PV modules show comparable electrical and mechanical performance to that of soldered cell modules, despite the fact that the ECA application is still rather early in its learning curve. The present study suggests that the novel ECA could lead to a promising alternative to the conventional soldering process and the more costly silver-filled ECAs.