Degradation Mechanism of Photovoltaic Insulating Backsheets Under the Stresses of UV Radiation and Temperature

The excessive use of traditional fossil energy is a major challenge, as it leads to the global energy crisis and climate change. Photovoltaic (PV) power generation technology opens up new opportunities to address these challenges. While the service lifetime of PV backsheets is around 25 years, a variety of stress factors can lead to premature degradation. In this study, the aging characteristics of PV insulating backsheets under two sequential stresses including ultraviolet (UV) irradiation and temperature were studied. The mechanism of degradation induced by UV and heat were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). These two methods are used to characterize the thermal properties and chemical composition of the samples, respectively. It can be found that the crystallinity increased after UV radiation exposure. Infrared spectroscopy indicated that there were some changes of chemical groups after UV exposure. Changes in crystallinity are more noticeable after UV irradiation as well as heat treatment, and changes in chemical groups are similar to those after a single UV treatment. In addition, breakdown field strength of samples was also measured in order to provide data support for aging state assessment. This research provides a meaningful insight to explore the degradation of polyethylene terephthalate (PET)-based backsheets.