Metallization is an essential step in the manufacture of mono-crystalline silicon solar cells. Optimization of contact materials maximizes photovoltaic efficiency. This study analyses the mechanisms of physical vapor deposition (PVD) metallization of a mono-crystalline silicon solar cell emitter, using an Ag/Al alloy as the back contact layer. Single-crystal silicon solar cell samples were prepared by vacuum evaporation with different silver and aluminum compositions. After rapid thermal annealing at temperatures of 400–700 ℃, the samples were characterized by XRD and SIMS to observe structural evolution and diffusion profiles. This study provides a better understanding of the metallization of mono-crystalline silicon solar cells with a view to optimizing yields. Physical vapor deposition (PVD) metallization was used for mono-crystalline silicon solar cells. The cells had a diameter of 10 cm and an initial thickness of 350 μm. The deposition was carried out in two stages: first 99.9999% pure aluminum, then silver powder, using the Joule-effect PVD technique in a vacuum. Four samples were prepared, one without annealing and three with different anneals at specific temperatures. Observations show that the silicon grains remain visible even after plating, indicating a very fine metallic deposit. The results reveal the controlled formation of an ohmic Ag2Al phase without damaging the polycrystalline silicon substrate. This study provides a better understanding of the metallization of polycrystalline silicon solar cells and paves the way for their optimization to achieve record efficiencies.