Effect of barrier property of backsheet on degradation of crystalline silicon photovoltaic modules under combined acceleration test composed of UV irradiation and subsequent damp-heat stress

The damp-heat test and the combined acceleration test composed of UV irradiation and subsequent damp-heat stress were conducted on multicrystalline silicon photovoltaic modules by changing the gas barrier property of a backsheet. In the damp-heat test, the deterioration greatly differed depending on the difference in the barrier property of the backsheet, whereas in the combined acceleration test, the degradation was less susceptible to the effect of such a difference. The difference in the manner of spreading deterioration between both tests was observed in electroluminescence images. From these results, it is considered that the degradation mechanism in the case of the combined acceleration test is different from that in the case of the damp-heat test.