Transmission electron microscope study of screen-printed Ag contacts on crystalline Si solar cells

Microstructural and chemical properties of screen-printed Ag contacts on an n+ emitter surface in crystalline Si solar cells are investigated using a transmission electron microscope. The Pb-based glass layer, where many Ag precipitates are randomly distributed, is formed between a Ag thick film and textured Si. For both textured and nontextured Si surfaces, the Ag crystallites are epitaxially grown on Si with an abrupt interface along the {111} atomic plane. Based on high resolution electron microscopy images combined with fast Fourier transform patterns, the registry of Ag on Si driven by a geometrical matching condition leads to minimization of the effective lattice mismatch between Ag and Si, resulting in the formation of a Ag/Si epitaxial superlattice near the interface region.