Electronic Transitions in Biaxially Oriented Polypropylene Accounting for Photo-Stimulated Currents

Biaxially oriented polypropylene (BOPP) is a widely used insulating material in capacitor films.As the demand for improved capacitor performance grows, it's crucial to have a deep understanding of polymer molecular structures and their electronic properties.Therefore, focusing on theoretical modeling, simulations, and experiments is important to uncover the relationship between microscopic phenomena and device effectiveness.In this study, we use a recently developed test bench coupling the Laser Intensity Modulated Method (LIMM) and Photo-Stimulated Discharge (PSD) measurements to investigate charge trapping and detrapping processes in BOPP samples.By analyzing photoinduced currents and absorption spectra, we identified relationships between foreign elements within the polymer chains and charge trapping and detrapping dynamics.Our research indicates that BOPP films typically display two light absorption bands in the UV-visible range.The generation of S1 excitons at around 3.1 eV may suggest the creation of free charges through the Auger effect and luminescence emission.Additionally, higher energy photons (~6.2 eV) may contribute to the formation of S2 excitons, influenced by chemical additives such as phenolic antioxidants, which can release electrons under the residual field associated with trapped space charge.