The Influence of the EVA Film Aging on the Degradation Behavior of PV Modules Under High Voltage Bias in Wet Conditions Followed by Electroluminescence

The influence of the ethylene-vinyl acetate (EVA) film quality on potential induced degradation was studied on in-house developed mini modules with p-type monocrystalline silicon solar cells. The modules were assembled with EVA films of equivalent qualities, but different ages and exposed to an accelerated test (relative humidity = 85%, T = 60 °C, V
_bias
= +1000 V). The age of the EVA film was determined from the time we received the EVA film, and opened the sealed enclosure and the time of lamination. After the EVA film was removed from the sealed enclosure, it was kept in a dark place at room temperature. The storage times of the “fresh,” “aged,” and “expired” films were: less than 14 d, around 5 mo, and more than 5 years, respectively. While modules with a “fresh” EVA film exhibit almost no degradation, the modules with the “aged” EVA film degrade very rapidly and severely. Their degradation rate was around 0.2%/d during the 2000 h of damp heat test. We also observed a strong silver line corrosion, which occurs because of the peroxide leftovers in the “aged” EVA films.