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

ABSTRACT 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°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.