Characterization of Glass Frit in Conductive Paste for N-Type Crystalline Silicon Solar Cells

Abstract

Contacting silver paste for an emitter of silicon solar cells has been pointed out to create shunting and to increase carrier recombination due to silver-crystallites at the emitter. However, since these observed electrical losses come of not only the crystallites but also multiple effects of constituents in the paste, whether the crystallites mainly cause these losses has still remained unknown. In this study, how glass frit “itself,” which is most important constituent in the paste, affects the electrical losses is investigated by applying the “floating contact method.” Furthermore, the contact interface between the frit and silicon surface is also investigated to elucidate the mechanism of the losses. The metal oxide glass frit itself is found to drastically cause the shunting and the recombination in n-type solar cells, resulting in loss in open-circuit voltage, and creates metal lead crystallites through redox reaction at silicon surface during firing. The shunting originates from the metallic lead, and the recombination is induced by diffused impurities or defects into the silicon emitter through the reaction. The electrical losses in the solar cells are led to not only by the silver-crystallites, but also by the glass frit itself.