Bismuth borosilicate-based thick film passivation of Ag grid for large-area dye-sensitized solar cells

A bismuth borosilicate glass-based thick film having a low glass transition temperature of 445°C was investigated as a passivation layer for protecting Ag-grid against corrosive reactions with the common I^-/I ₃^- electrolyte for large area dye-sensitized solar cells (DSSC). Glass paste was carefully screen-printed and then fired in the temperature range of 480°-540°C to have a final thickness of ∼4 μm. The effectiveness of the glass passivation film was related to the degree of densification or porosity, which depended on firing temperature of the glass. A high optical transmittance of ∼70% and the chemical inertness of the well-densified glass film can be highlighted as promising characteristics for this passivation application. The low electrical resistance of ∼27 Ω of the fluorine-doped tin oxide-coated substrate, which was obtained by patterning Ag grid, remained stable over the exposure period of ∼10 days in the electrolyte only when the hermetic protection of Ag was secured by the glass overcoat film after densification at 540°C.