Topological evolution and dynamic wetting of glass frits for laser-enhanced contact optimization in TOPCon solar cells

Laser-enhanced contact optimization (LECO) is an important technology for making high-efficiency n-type TOPCon solar cells. In this study, we tested six different Te/Pb molar ratios (0–0.5) to determine how the glass microstructure, thermal properties, and cell performance are related. Using Raman, XPS, and DSC analyses, we found that the glass structure changes in stages, depending on the arrangement of Te atoms. At lower Te/Pb ratios, Te mostly forms asymmetric [TeO 3 ] units. The lone-pair electrons in these units create more space in the glass network, reaching the highest level of network breakdown at a ratio of 0.25. When the ratio increases, the network becomes denser as more [TeO 4 ] units form. This change affects the glass's thermal properties, with the 0.25 ratio showing the lowest glass transition temperature and a wider sintering window. High-temperature microscopy shows that these features help the glass evenly wet the SiN x /AlO x passivation stack. We also examined how altering the Te/Pb ratio affects the structure and high-temperature wetting of LECO-specific Pb-B-Si glass frits. The improved flow of the glass helps form a continuous layer at the interface, which supports the growth of dense silver crystals and many current-fired contacts (CFCs). As a result, the frit with a 0.25 Te/Pb ratio gives a 0.21% boost in efficiency and lowers series resistance by 0.23 mΩ. However, too much Te causes problems such as junction shunting and over-etching, indicating a critical processing range. This study explains how microstructure affects frit performance and offers a precise approach to improving photovoltaic metallization.