9:15 AM - 9:30 AM
[19a-W321-2] Degradation Mechanisms of c-Si PV Cells Exposed to Acetic Acid Vapor under Hygrothermal Conditions
Keywords:photovoltaic cell,reliability,front electrode
A major degradation cause of c-Si PV modules installed in hot-humid climate has been elucidated as the current collection failure induced by the corrosion in finger electrodes on the PV cells. For this corroding mechanism, it has been recently proposed that acetic acid liberated from EVA in the PV modules at hygrothermal conditions would dissolve the glass layer which is stacked between Ag bulk layer within finger electrodes and emitter surface, then the gaps underneath finger electrodes would be formed by this dissolution of glass layer. We tried to detect the electrical signal concerned to this gap formation, because this signal seems to be a crucial “aging signature” which is able to easily observe even in PV module. And, the extreme increasing in resistance caused by a novel-developed capacitor, which was synchronized with the intense decrease in FF, was detected by AC impedance spectroscopy in bare c-Si PV cells exposed to acetic acid vapor, and the similar electrical signals were observed also in c-Si PV modules exposed to damp heat stress in long-term. Based on the detailed analysis in these phenomena, the degradation mechanisms of c-Si PV module under hygrothermal conditions are discussed, to contribute the lifetime prediction of PV modules installed in such condition.