Evaluation of Energy Level Distribution in Nanocomposite Based on Polarization Current

In this paper, from the perspective of the change of energy level distribution in the polymer after filled with nanoparticles, a method for the evaluation of energy level distribution in nanocomposite was deeply investigated by analyzing the polarization current. And the feasibility of the method was verified by the characteristics of space charge accumulation. High voltage DC potential was applied on the LDPE/SiO2 nanocomposites with filling concentrations of 0.0, 0.5, 2.0 and 5.0 wt% to measure the polarization current, respectively. The electric field ranged from 1 to 90 kV/mm. The characteristics of quasi-steady current were analyzed based on Space charge limited current (SCLC) theory. As the filling concentration increased, the threshold electric field at which the traps were filled dropped and then rose. The threshold electric field was related to the total trap density, and it could be deduced that the total trap density decreased first and then increased as the concentration increased. It was found that the effect of filling concentration on transit time at which the current tended to be steady was consistent with its effect on the threshold electric field. A method for qualitatively evaluating the trap energy density based on polarization current was proposed on this basis. In order to verify the rationality of the method, a space charge measurement was carried out. The effect of filler content on total trap density obtained from the charge accumulation characteristic was consistent with the result of the polarization current.