Charge Mobility in Biaxially Oriented Polypropylene Films

Abstract

High electric field may cause the leakage current in Biaxially Oriented Polypropylene (BOPP), which will result in the energy losses and the reduction of the energy efficiency when BOPP used as the dielectric of the capacitors. Therefore, it is important to investigate the charge dynamics in BOPP. Meanwhile, charge mobility is an important element of the charge dynamics. Consequently, in this investigation, charge mobility in the BOPP films under various operating DC electric fields was studied by the leakage current method and the transient current method. The leakage currents were recorded under the electric field from 200kV/mm to 450kV/mm. The J-V characteristics in a log-log plot clearly shows two linear parts, which are corresponding to the trap-filled limit (TFL) regime and the trap free regime, the TFL regime ended by the transition voltage V TFL . It is the characteristics of space charge limited currents (SCLC), and the mobility of charge in TFL regime is about 10−15cm2V−1s−1. In previous study, the calculated mobility based on the underdamped short-circuited current is about 10−9cm2V−1s−1 on average. The great difference of mobility under the two conditions is considered to be attributed to the charge distribution, which decides the charge dynamics to a certain degree.