The Electroluminescence And Current Measurement Of PET Films Under High DC Electric Field

Electroluminescence (EL) is a phenomenon transforms electrical energy into optical energy directly, and it has close relation with space charge. It is said that EL can help to understand the injection, transport and storage of charge, to interpret the threshold of electrical aging and the mechanics of energy dissipation in polymer. And it can provide some supports for monitoring the aging rate of polymer.Because of its complexity, there is no merchantable product of high electrical field EL measurement set-up worldwide. An extreme high electrical field EL measurement set-up was first established domestically in the Harbin Universty of Science and Technology, which was supported by major project of National Natural Science Foundation.The EL intensity, current and spectrum of the poly (ethylene terephthalate) (PET) films were tested under high dc fields. The result shows that the light intensity of PET films increases along with the electrical fields, the light intensity is close to the background noise when the field is lower than about 2.0MV/cm, the light intensity increases slowly with the increasing of the electrical field when the field is higher than about 2.0MV/cm, but when the field is near or higher than about 3.5MV/cm the light intensity increases quickly, then the films would be breakdown when the field even higher. The current of PET films increases along with the electrical fields and the threshold is about 2.0MV/cm. It shows that the aging threshold of PET films is about 2.0MV/cm and its pre-breackdown threshold is about 3.5MV/cm. The EL spectra have peaks about 300～400nm, 400～460nm, 500～600nm and 680nm, the peaks between 500nm and 600nm is higher. The peak of 680nm increases quickly after the pre- breakdown phenomenon. In order to value the dielectric characters of the PET films, this paper analyzed the experimental datas by two-parameter Weibull distribution, and found out the life length, the accumulative dead probability of the breakdown field and the reliability equation under the voltage power increased step by step at (24±1)℃. After the verification of assumption, it's found that the experimental results submit Weibull distribution. The medium values of the life length and the breakdown field are 409.2 minutes and 3.8MV/cm, separately.