Efficient Metallization of P‐Type Polysilicon in Bifacial TOPCon Structure Silicon Solar Cells Enabled by Ag–Ga Alloy

The development of bifacial tunnel oxide passivated contact (TOPCon) structure crystal silicon (c‐Si) solar cells presents significant challenges, particularly regarding the metallization of p‐type polysilicon (poly‐Si (P)). The Al‐containing Ag paste to achieve low contact resistivity atop poly‐Si (P) may generate Ag–Al super spikes after sintering, penetrating the poly‐Si (P) and degrading surface passivation. This study investigates gallium (Ga) as an alternative element alloying with Ag for poly‐Si (P) metallization by mimicking screening‐printing conducting paste with a facile thermal evaporation process at the proof‐of‐concept level. The enhanced doping concentration on the poly‐Si (P) surface due to the Ga diffusion and the GaO x interlayer with high negative fixed charge density would facilitate the transport of holes from poly‐Si (P) to the metal electrode, resulting in a low contact resistivity of 1.72 mΩ cm 2 . Besides, since the solid solubility of Si in Ga is significantly lower than that in Al, it is highly likely to avoid any overly grown spikes at the high‐temperature sintering process. These findings provide valuable insights for developing effective poly‐Si (P) metallization strategies in bifacial TOPCon structure c‐Si solar cells by incorporating Ga into industrial screen‐printed pastes.