Influence of surface near doping concentration on contact formation of silver thick film contacts

We investigate the properties of silver thick film contacts on phosphorus doped alkaline textured silicon surfaces with varying surface doping levels. Using scanning electron microscopy, we find that the surface near doping concentration influences the formation of silver crystallites especially those that are in direct contact with both the silicon surface and the contact finger. The observed correlation between direct silver crystallite imprint coverage and specific contact resistance allows for extracting the specific contact resistance of individual crystallites to be approximately 3.3 µO cm2, which agrees well with theoretical predictions. Furthermore we present a new approach that allows for a quantitative separation of direct and indirect current conduction channels. For our experimental conditions, the assumption of current conduction exclusively by transport through silver crystallites adequately describes the experimental data. Finally we fabricate bifacial n-type solar cells with peak efficiencies of 19.9%.