Microstructure beneath screen-printed silver contacts and its correlation to metallization-induced recombination parameters

Abstract

In this work, we present an approach to model metallization-induced recombination losses j 0,met of screen-printed fire-through metallization pastes, which are used e.g. for the contacts on the front side of passivated emitter and rear cells (PERC). Modelling is based on the local phosphorus emitter doping profile and the local microstructure of the interface between metal contact and silicon surface, which is characterized during a quantitative microstructural analysis using the scanning electron microscope (SEM). By comparing the modelled j 0,met to measured j 0,met results determined at the same position of both, the microstructural analysis and emitter doping profile, we find that in most cases recombination is dominated by the etch back of the emitter by the glass frit rather than by penetration of crystallites into the doped region. However, for crystallites protruding deep into the emitter or rather up to the junction, recombination at the crystallites becomes significant as well. Our modelled results yield indications that the etch depth into the emitter doping profile by the glass frit contained in the metallization paste, is sensitive to the emitter doping profile itself. • Metallization-induced recombination is dominated by the etch back of the emitter doping profile • Etch back of the emitter doping profile is sensitive to doping profile itself • Plating useful to enhance contrast for microstructure analysis