Investigation on the Effect of Accumulated Charge-Induced Degradation on Multilayer Photovoltaic Insulating Backsheets Based on Atomic Force Microscopy

As a clean and renewable energy, solar energy has drawn people’s attention to mitigate the energy crisis around the world. A solar photovoltaic (PV) system is a reliable way to collect solar energy whose service lifetime is usually shorter than the designed time because of accumulated charge-induced degradation caused by electrical aging. With the rapid development of PV systems, the traditional polyethylene terephthalate (PET) backsheet cannot meet the requirements of insulation and package for the advanced solar energy system. In this context, two different backsheet materials, namely, KPK (polyvinylidene fluoride, PET, polyvinylidene fluoride) and TPT (polyvinyl fluoride, PET, polyvinyl fluoride), were selected to explore accumulated charge-induced degradation caused by partial discharge (PD) and corona discharge. In this paper, the backsheets were electrically stressed for 30, 60, and 120 min by PD and electrically stressed for 10 min by corona discharge. The accumulation and transportation of charges were investigated by phase-resolved partial discharge (PRPD) and surface potential decay (SPD). At the same time, the topography of KPK and TPT determined using atomic force microscopy after PD activity was also investigated. The explorations of PD activity showed that KPK and TPT have a similar PD resistance, but their SPD were entirely different after corona discharge. The research works in this paper provide an important path to investigate the aging process of insulating polymers and evaluate the lifetime of insulating backsheets of PV modules, as well as a guidance to improve the testing standards for the PV system.