Formation of Local Rear Contacts Stimulated by Al-Si Interdiffusion within Different Al Grid Widths

We propose a physical mechanism that explains the local contact formation stimulated by the aluminum-silicon (Al-Si) interdiffusion within the various widths of Al rear grid for bifacial-passivated emitter and rear cell (Bi-PERC). The rear sides of Bi-PERCs were screen-printed with thin fingers (< 100 mu m) or wider fingers aligned directly on the contact sites. From the elemental mapping analysis results, the following conjecture was confirmed: rear metallization structure has a direct impact on the local contact formation, particularly on the thickness of aluminum-back surface field (Al-BSF), and microstructures of alloy formed. A thicker Al-BSF partly results in an increase in open-circuit voltage of Bi-PERC. The wider Al finger leads to a slight improvement in fill factor of a cell.