Abstract
The hetero charge accumulated in Polyimide film, which was increased with increasing applied electric field, was observed by PEA equipment. In order to explain the mechanism of hetero charge accumulation depending on electric field, we proposed a new model combined Fermi-Dirac function (the electron-hole pair generation probability between band gap (about 2.5eV) of HOMO and LUMO under thermally equilibrium condition, which was obtained by Quantum Chemical Calculation) and Pool-Frenkel effect (the electron-hole pair generating probability affected by local electric field). In the process of electric charge transfer, the electron carrier is stayed at deep trap site (the molecular part of one benzene ring with imide groups) and the hole carrier is able to drift between shallow trap sites (the molecular part of ether bond between two benzene rings). From the different transfer properties between electron and hole, we could explain the mechanism of hetero charge accumulation in Polyimide film under high electric stress.
