Charging and discharging currents and photocurrent transient and polypropylene with the presence of a gas gap between the specimen and the electrodes

The photocurrent transient has been measured during the decay period of the dark charging current in polypropylene both with and without exciting radiation from a series of light pulses from an ultraviolet (UV) lamp or an He-Ne laser beam, using arrangements with and without a gas gap between the specimen and the electrodes. The results show that the charging current for polypropylene decays with time much faster for the metallic electrode separated from the specimen with a gas gap than that for the electrodes in intimate contact with the specimen. The photocurrent depends on the magnitude of the charging current and also on the presence of the gas gap. Analysis of the experimental results indicates that the decay of the dark charging current is associated with the time-dependent trapping and detrapping processes and that both electrons and holes can be injected from electrodes.<>