Toward Understanding of Charge Transport Behavior in Polymeric Insulating Material Through Surface Potential Decay Measurement Depending on Capture Cross-Section Estimation

摘要

The space charge accumulation in the polymeric materials under DC electric field can distort the electric field and lead to the breakdown of the polymeric materials. The understanding of charge transport behavior is therefore a fundamental work for the safe use of the polymeric material. In this contribution, attempts have been made to identify the charge transport mechanism by surface potential decay (SPD) measurement through the estimation of capture cross-section via both experimental and numerical simulation methods. Low density polyethylene (LDPE) film with the thickness of 110 µm was prepared as the test sample. The SPD test was carried out at 20 °C with relative humidity lower than 25%. In addition, the bipolar charge transport (BCT) model was applied to simulate the SPD process of the LDPE and the electric field within the sample was calculated. The capture cross-section of the trap in the sample was extracted as well, by which the charge transport mechanism was tentatively identified. According to the simulation results, with the same trap density, as the cross-section of trap in the sample is large, the probability of the charge captured by the trap is high, the charge follows the hopping conduction. As the trap cross-section is small, the probability of the charge captured by the trap is low, the charge transport should be attributed to the Poole-Frenkel conduction. The threshold value of capture cross-section for the different transport manners was estimated with the simulation method by using the SPD data. It can provide researchers with an optional theory that can be used to understand the charge transport mechanism in the polymer.