Enabling EVA for TOPCon: How Glass Frit Composition Governs Resistance to Acetic Acid-Induced Corrosion

Laser-assisted firing (LAF) technologies, such as laser-enhanced contact optimization (LECO), have enabled the reliable application of low-Al Ag pastes for front-side metallization in tunnel oxide passivated contact (TOPCon) solar cells, opening a pathway to improved damp-heat (DH) stability and glass-backsheet (G-B) module designs. To further lower production costs, ethylene-vinyl acetate (EVA) and EVA/polyolefin/EVA (EPE) encapsulants are commonly employed; however, their long-term hydrolytic degradation produces acetic acid, which promotes metallization corrosion. In this work, we systematically investigate the impact of glass frit chemistry in two commercial low-Al content Ag front pastes on the cell- and module-level stability of LAF-processed TOPCon devices. Accelerated acetic-acid exposure tests reveal that a Ba- and Zn-modified glass frit (Paste B) exhibits markedly improved resistance to interfacial degradation compared with a Pb- and B-rich frit (Paste A), as evidenced by a maintained series resistance, contact resistivity and Ag-Si interfacial integrity. Microscopic and elemental analyses revealed that Ba enrichment in the glass frit markedly improves interfacial stability relative to Pb- and B-rich formulations. At the module level, DH85 (85 degrees C/85% RH) testing of G-B TOPCon modules (front EPE/rear EVA) demonstrates that Paste B limits the relative power loss to 4%-5% after 1500 h, whereas Paste A leads to severe fill-factor-driven degradation resulting in a power loss over 25%. These results establish a direct correlation between glass frit composition, acetic-acid corrosion resistance and DH stability, highlighting glass network engineering as a key lever for designing robust, low-cost metallization systems for next-generation TOPCon modules.