Nano-size Joule-Heating to Achieve Low-Ohmic Ag-Si Contact on Boron Emitters of n-TOPCon Solar Cells.

Over the past decade, Tunnel Oxide Passivated Contact (TOPCon) solar cells have emerged as a leading technology for high-efficiency silicon solar cells. Conventional metallization processes using silver/aluminum (Ag/Al) pastes encounter significant hurdles due to reliability risks and insufficient contact quality. Recent advancements in laser-induced metallization technologies, particularly laser-enhanced contact optimization (LECO), offer promising solutions. However, the mechanism of silver-silicon (Ag-Si) contact formation on the P+ emitter of TOPCon cells via LECO processing remains incompletely understood. This study designs and prepares two types of glass frits (GF-A and GF-B) for TOPCon cells and investigates the electrical properties of corresponding devices. Advanced techniques are employed to examine the Ag-Siinterfaces. The results demonstrate that GF-A-based TOPCon cells (Cell-A) outperformed GF-B-based cells (Cell-B) due to the construction of a current-confined Ag-Si interface. A composite conductive model for the Ag-Si interfaces by LECO treatment is introduced, revealing the nano-size Joule-heating to achieve the Ag-Si eutectic structure as the underlying formation mechanism. This work contributes to the understanding of metal-silicon contact optimization in solar cells and introduces novel methodologies for laser-induced synthesis and micro-nano interface engineering.