Mitigating Passivation Layer Damage and Lowering Contact Resistivity of TOPcon Solar Cells Through Low PbO Content Ag Paste

The development of front-side pastes suitable for devices with high sheet resistance such as tunnel oxide passivated contact (TOPCon), is of great significance but remains a considerable challenge. The optimization of the Ag-Si contact interface is crucial for enhancing contact and improving the efficiency of these devices. This work investigates the front-side Ag pastes with low Al content (<2 wt.%) and different frit compositions for TOPCon. It is found that the paste with low-addition frit effectively prevents excessive etching of passivation layers and minimizes additional damage to boron emitters while ensuring favorable contact. Meanwhile, the lowly FT (fire through) paste promotes Ag nanoparticles with larger particle sizes and higher quantities in the interfacial glass, thereby enhancing the conductivity of the interfacial glass and reducing contact resistivity. A low contact resistivity of ≈1 mΩ·cm² and superior photovoltaic conversion efficiency of 25.19% are achieved on TOPCon with a sheet resistance of ≈350 Ω/□. This work demonstrates the application potential of Ag-Al paste with low Al content suitable for high sheet resistance emitters by modulating the Ag-Si interface structure. The coupling between microstructure and device performance is elucidated offering an innovative approach for developing silver paste suitable for high sheet resistance TOPCon.