Nanoscale electron transfer mechanism in metallized polypropylene films

Abstract

Metallized biaxially oriented polypropylene (BOPP) films are widely used in electronics and electrical power systems. However, as the demand for metallized films (MFs) with enhanced properties increases across various applications, studying the micro-level electron transfer mechanisms has become a promising approach to regulate the electrical characteristics of the metallized films. In this work, we systematically investigated the surface electron transfer mechanism, space charge distribution injected from external electrodes at the nanoscale, and macro-level electrical characteristics in different MFs. Results revealed that the MFs with thinner metallized layers exhibited greater surface charge accumulation, slower dissipation and reduced charge injection into the dielectric layer, thereby affecting the dielectric constant, leakage current, breakdown property and self-healing characteristics of the samples. We employed tunnelling current measurements using atomic force microscopy (AFM) to calculate the energy barrier height in different metallized films for studying the influence mechanism of the metallized layer thickness and the introduction of BaTiO₃. These results established a relationship between electron transfer at the nanoscale and macro-level material electrical properties of different BOPP metallized films. Additionally, the results of space charge testing indicated that the accumulation amount of space charge determined the energy storage capacity of the MFs, and at the same time, a bipolar carrier simulation model was developed to validate the electron transfer mechanism. The simulation results aligned well with the experimental findings, further confirming the influence of the BaTiO₃ composite layer on nanoscale charge transfer dynamics.