Investigation of Charge Injection in Gas-Impregnated Polyethylene by Measurement of Electroluminescence under AC Voltage

Abstract

Electroluminescence (EL) in polyethylene (PE) impregnated with N 2 , O 2 or SF 6 gas has been measured under ac voltages to investigate the effect of impregnation gas on charge injection. EL is strongly dependent on the processes of electron injection and transport in the surface region of PE. The results of our measurements of EL indicate that the process of electron injection is greatly affected by the type of impregnation gas in PE. In particular, O 2 gas which is electronegative and chemically reactive markedly affects the charge injection process, causing a reduction in EL inception voltage and barrier height at the electrode-polymer interface. The surface states induced by the presence of O 2 gas or by oxidation of PE enhance the electron injection. However, electrons injected into such surface states likely contribute little to EL. N 2 gas also causes a reduction in the EL intensity but does not induce a change in the EL inception voltage and the barrier height in comparison with those in the degassed case. N 2 gas probably affects an electron transport process such as intermolecular conduction in the surface region of PE rather than the electron injection process.