Effect of Surface Defects on Field-Induced Hot-Carrier Chemistry in Dielectric Polymers

Performance of dielectric polymers under high electric field is limited by the electrical breakdown, which is commonly understood as an avalanche of processes such as carrier multiplication and defect generation. We model the hot-carriers transport in dielectric polymer, polyethylene, with excited-state quantum molecular dynamics simulations in presence of electric field, which reveal multiple microscopic processes induced by hot electrons and holes under an electric field. The key chemical damage occurs due to localization of holes at the surface of slab which weaken carbon-carbon bonds on the surface. Introducing surface defects alter the valenca-band maximum (VBM) state in polyethylene leading to bond breaking at lower field. Further, we have isolated C-C bond lengths and VBM localization as a proxy for dielectric breakdown. Such proxies allow us to perform one simulation to understand the effect of defect rather than scanning the complete electric field range. Such quantitative and qualitative information can be incorporated into first principles-informed, predictive modeling of dielectric breakdown.