Influence of Module Architecture and Humidity on Local Module Degradation

Moisture ingress is an established issue for photovoltaic module durability. Durability studies probing moisture effects typically evaluate performance losses at the module level, attributing global power losses to the overall humidity condition of the test environment while leaving local module behavior unknown. We leverage our recently published optical moisture quantification method (water reflectometry detection, WaRD) and biased photoluminescence imaging to spatially correlate module moisture content and cell performance over the course of accelerated damp heat tests. These tests, carried out on glass-glass and glass-backsheet module packages at various temperatures and humidities, reveal two dominant modes of local cell performance loss - acute finger interruptions and global series resistance (R
s
) increase. We show that acute failures are more prevalent in glass-glass packages and not influenced by local module moisture dose, and that background R
s
increase is greatest in glass-backsheet packages at higher humidity conditions.