Mechanisms of electroluminescence during aging of polyethylene

Abstract

The study of electrical aging of polyethylene subjected to a 50 Hz ac voltage has shown that electroluminescence occured in the bulk of the polymer. These light emissions (detected in the visible range of wavelength) were due to the buildup of space charge around the electrodes. In a previous paper [J. Appl. Phys. 5 4 , 1532 (1983)] results concerning the role of dissolved gases in polyethylene were presented, where particular attention was paid to electroluminescence effects. The present work aims to answer the two following questions: (1) what are the mechanisms causing the electroluminescence? (2) what is the nature of the luminescent centers? Study of the light emission with respect to the applied voltage form, the frequency, (when ac voltage is applied) and the voltage amplitude, shows that the light emission is due to radiative recombinations of carriers injected through the metal‐dielectric interface following the Fowler–Nordheim effect. This process requires a double injection of carriers. The influence of electrode material on the light emission intensity is then shown, which is in good agreement with the injection mechanism proposed. The luminescent centers are carriers stabilized by deep traps in the polyethylene.