Enabling 748.6 mV Open‐Circuit Voltage in Industrial Bifacial Tunnel Oxide Passivating Contact Solar Cells With Multi‐Layer Polysilicon and Tailored Silver Paste

ABSTRACT Although tunnel oxide passivating contact (TOPCon) solar cells have become a leading photovoltaic technology, the traditional single‐layer polysilicon (poly‐Si) structure remains a critical challenge in balancing parasitic absorption, passivation performance, and firing‐through degradation. To address this issue, we propose an ultrathin three‐layer poly‐Si stack (60 nm) separated by ultrathin SiO x interlayers, combined with a tailored rear silver paste. Notably, the outer poly‐Si layer with higher phosphorus doping facilitates electrical contact during firing‐through, while the inner poly‐Si layer with lower phosphorus doping exhibits higher crystallinity, facilitating passivation quality; meanwhile, the intermediate‐buffer poly‐Si ensures strong robustness. Moreover, a specific silver paste formulation with low corrosivity and excellent rheological properties enables the formation of low‐contact resistance. The resulting TOPCon devices achieve a certified efficiency of 26.07% and an exceptional open‐circuit voltage of 748.6 mV, representing a milestone approaching that of silicon heterojunction cells. Moreover, this design effectively reduces parasitic absorption, yielding a high bifaciality of 88.6%.