Effect of wettability and thermal properties of glass frits on the interconnection reliability of solar cell busbars

Abstract

Increasing the interconnection reliability of the busbars in Tunnel Oxide Passivated contacts (TOPCon) solar cells is essential for optimizing the stability of photovoltaic (PV) modules interconnection. The bonding at the PV ribbon/busbar/c-Si (Sn/Ag/Si) interface directly determines the solderability of the busbars in solar cells, thus directly affects the interconnection reliability. It was found that the bond strength between the Sn/Ag/Si interfaces is intricately linked to the properties of the glass frits. To reaching the optimal soldering results necessitates a thorough comprehension and meticulous regulation of the characteristics of glass frits. Taking Pb-B-Si based glass frits as an example, this work changed the properties of the glass frits by adding additional oxides. The impact of glass frits on the adhesion at the Sn/Ag/Si interface was thoroughly investigated through etching experiments and observation of intermetallic compound (IMC) growth, resulting in enhanced soldering tension. Further discussed the relationship between the soldering tension of the busbar of TOPCon solar cells and the properties of the glass frits. The results showed that the softening temperature, high-temperature viscosity and wettability of the glass frits could all affect the interconnection reliability of the busbar in solar cells. Furthermore, controlling the downward flow of the molten glass phase during the sintering process of the Ag paste was also crucial for improving the interconnection reliability of the busbars.