Ultra-violet degradation behavior of polymeric backsheets of photovoltaic modules

This study is designed to understand the ultra-violet (UV) degradation of polymeric backsheets used in PV modules. Commercial photovoltaic backsheets from four suppliers were UV-aged for up to 3000 hours. The aged samples were tested using optical microscopy, scanning electron microscopy (SEM), shrinkage rate test, color measurements, UV-Vis-NIR, Fourier transform infrared spectroscopy (FTIR), and dielectrical tests to study the microstructural, color, chemical and electrical properties. Yellowness Index (YI) and Delta E were used to quantify the color changes which were found in strong correlation with FTIR results. The characters of the surface cracks generated were found to be affected by degree of UV degradation and polymer chain alignment of the backsheets. Electrical properties were not significantly affected by UV irradiation. The results suggest insufficient UV aging time designated in current PV module test standard. A longer aging time is recommended for quality assurance.