Low-filled electrically conductive adhesives based on silver-coated glass and copper particles

Replacing silver in solar module production is the hot topic in metallization and interconnection development. Whereas in metallization mainly silver-coated copper is utilized, the lower electrical requirements for cell interconnection, open up the opportunity to utilize particles with non-conductive cores as well. This study focuses on the development and characterization of an electrically conductive adhesive (ECA) for the shingled cell interconnection based on silver-coated glass and silver-coated copper particles, respectively. The formulated low-filled ECAs were stabilized against sedimentation using a halogen-based additive. The silver-coated glass particles show good compatibility with the utilized epoxy resin. Employing a mixture of silver-coated glass particles and silver flakes, the silver content in the ECA can be reduced to 25 wt% and the mechanical properties can be adjusted by the fraction of glass particles used. In shingled modules such an ECA shows the same stable performance as the reference based on pure silver particles. An ECA with only 7 wt% silver was formulated using silver-coated copper particles meeting all requirements for solar cell shingling. Shingled modules build from such an ECA show promising initial efficiency. Damp heat 500 was passed comparable to the silver reference, indicating oxidation stability. However, degradation during accelerated thermal cycling 200 is believed to originate from remaining issues with curing. This study shows, that by carefully adjusting polymer, particles and additives the silver consumption in ECAs can be significantly reduced without any losses in interconnection performance.