聚丙烯载流子输运与能量积累调制直流击穿威布尔分布特性仿真研究

Polypropylene is widely used in thin-film capacitors for its excellent electrical and chemical properties. However, the dielectric breakdown under DC electrical field is the key factor restricting the improvement of the energy storage density of capacitors. Under the action of the external strong electric field, the charge injected from the electrode/dielectric interface is driven by the electric field force to transport and accumulate energy, forming leakage current, accumulating space charge, and distorting electric field, which eventually leads to the breakdown of the dielectric. Based on the physical process of dielectric breakdown caused by carrier transport and energy accumulation, six characteristic parameters of charge transport, including charge injection barrier, attempted escape frequency, carrier mobility, trap energy level, trap density, and trap capture probability, are extracted. The charge transport characteristic parameters are set as random variables, and the carrier transport and energy accumulation process are simulated by carrier transport and molecular displacement modulated electrical breakdown model. The calculated breakdown strength follows Weibull distribution. The relationship between Weibull characteristic electrical breakdown strength and shape distribution parameter with the variance of different charge transport random variables is established: with the increase of variance, the characteristic electrical breakdown strength is basically stable near the experimental value, and the shape distribution parameter decreases due to the increase of dispersion of breakdown data. Comparing the relationship between the variance of transport parameters and Weibull distribution, it is found that Weibull distribution has a strong dependence on trap energy level, a weak dependence on escape frequency and mobility, and the weakest dependence on injection barrier and trap capture probability. The results explain the mechanism of charge transport random variables changing the breakdown Weibull distribution by regulating carrier transport and energy accumulation.