Simulation of Carrier Transport and Energy Accumulation Modulated DC Breakdown Weibull Distribution in Polypropylene

doi:10.11985/2021.02.007

Abstract

Abstract:

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.

Key words: Weibull distribution of DC breakdown, shape distribution parameter, charge transport random variables, carrier transport and energy accumulation, chain displacement and free volume expansion

CLC Number:

TM85

CAI Shurao, GAO Ziwei, JI Minzun, YAO Jiachi, LI Pengxin, MIN Daomin, LI Shengtao, WU Qingzhou. Simulation of Carrier Transport and Energy Accumulation Modulated DC Breakdown Weibull Distribution in Polypropylene[J]. Journal of Electrical Engineering, 2021, 16(2): 50-59.

Figures/Tables 10

References 25

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参数	期望值
温度T/℃	33
样品厚度d/mm	100
升压速率k_ramp/(V/s)	2 000
相对介电常数ε_r	2.3(1 MHz)
陷阱能级E_T/eV	0.86
陷阱密度N_T/m^-3	1.0×10²¹
陷阱捕获概率P_tr/s^-1	0.085
试图逃逸频率v_ATE/s^-1	1.727×10⁸
注入势垒ϕ_in/eV	0.86
载流子迁移率μ₀/(m²·V^-1·s^-1)	1.0×10^-13

数值	威布尔参数
数值	α/(kV·mm^-1)	β
试验值	281.5	17.0
计算值-σ(E_T)=0.005	287.0	17.3