Enhanced Passivation of Boron-Doped Polysilicon Passivated Contacts With a Single-Sided J₀ of 2.8 fA/cm² by...

Boron (B)-induced interface defects remain a key bottleneck that limits the passivation quality of p-type tunnel oxide passivating contacts (TOPCon), thereby constraining the efficiency of back-contact TOPCon (TBC) solar cells. Here, we introduce a dual-layer silicon oxide (SiO_x) design that forms a SiO_x/p⁺ poly-Si/SiO_x/p⁺⁺ poly-Si passivation structure. The additional SiO_x layer effectively mitigates interlayer stress, preventing blistering during high-temperature annealing, and increases interfacial hydrogen concentration to suppress defect states. Through systematic optimization of the preparation and annealing conditions of the outer SiO_x layer, the p-type TOPCon structures achieve outstanding passivation on n-type wafers, with a single-sided recombination current density (J_0,s) of 2.8 fA/cm² and an implied open-circuit voltage (iV_oc) of 741 mV. This represents one of the best results reported to date, surpassing the current industrial records. Compared with the previous single-layer SiO_x designs, this configuration delivers a substantial improvement of passivation while simultaneously enabling a reduced poly-Si thickness. Numerical simulations further demonstrate a 0.18% absolute efficiency gain in TBC cells with the dual-layer structure compared to single-layer configuration. This work demonstrates that a dual-layer SiO_x architecture effectively lowers interface defect density and enhances p-type TOPCon passivation, underscoring its significant potential for industrial application in high-efficiency TBC cells.