Peak firing temperature dependence of the microstructure of Ag thick-film contacts on silicon solar cells - a detailed AFM study of the interface

The main purpose of the presented investigation was to clarify the firing temperature dependence of the contact microstructure at the interface of Ag thick-film contacts on silicon solar cells by means of in-plane atomic force microscopy (AFM) measurements. The measured electrical properties of the contacts are compared with the Ag crystallite density at the Si interface. A negative correlation of the Ag crystallite density and the specific contact resistance could be shown. The specific contact resistance is calculated using a newly proposed model of the current flow across the contact interface. The study strongly supports the model of local current paths across the contact interface as being the determinant transport mechanism and improves the fundamental knowledge on screen printed Ag thick-film contacts, which will be required to design the next generation of Ag pastes for highest efficiency silicon solar cells.