Determination of Parameters for Space Charge Simulation Based on Bipolar Charge Transport Model Under a Divergent Electric Field

The space charge dynamics inside insulating materials under divergent electric fields are commonly studied by simulation with the bipolar charge transport model. The model parameters have a significant impact on the simulated space charge distributions. In this article, a method for determining the model parameters based on a comparison of experimental and simulation results is proposed. Based on the pulsed electro-acoustic theory, the acoustic signals induced by the space charge injected from a needle electrode are measured. To simplify the comparison, two characteristic values indicating the delay and amplitude of the charge acoustic signal are proposed, which can reflect the properties of the space charge distribution. To evaluate the model parameters, a simulation model identical to the experimental sample is established, and the space charge injection process is simulated. The influences of the key model parameters, which are injection barrier height, carrier mobility, trapping coefficient, and detrapping coefficient, on the simulated space charge distributions and characteristic values of the acoustic signals are investigated. According to these influence rules, the model parameters are finally determined so that the simulated acoustic signals match well with the experimental ones, which means that the simulated space charge distributions show a good representation of the real situation.