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Polyamide (PA)-based backsheet as an emerging product has been developed in recent years to partially substitute fluoropolymer materials under the intensified cost-reduction pressure. However, a number of reports indicate that backsheet cracks have been observed in fielded modules in a few locations after only a few years of exposure. An in-depth analysis on degradation and crack formation and their dependence on climatic conditions is needed. In this work, the field PV modules with PA-based backsheet under five different climatic conditions up to six years were retrieved and analyzed, including humid subtropical climate (Changshu, China), dry-summer subtropical climate (Rome, Italy), marine west coast climate (Bergamo, Italy), desert climate (Arizona, United States) and tropical climate (Thailand). Macroscopic cracks in backsheet were observed for modules aged in Italy and Thailand, while only hairline cracks showed up in backsheet from Changshu, and no cracks could be seen in Arizona. Backsheet in Changshu also experienced much higher yellowing than other sites, while the gloss loss of the backsheet in Italy is the highest. Spectroscopic analyses were also performed to identify various degradation products and to understand the possible changes in degradation mechanism of backsheets under different climates. The intercorrelations between various degradation modes of PA-based backsheet and weathering factors will be further established, providing a valuable information on the material selection and lifetime prediction for the backsheet.
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