Effects of electrodes on space charge in polypropylene

We investigated the effects of electrodes, i.e. Al plate, semiconducting (SC) layer and evaporated Al, on space charge in polypropylene (PP) by using the pulsed electroacoustic (PEA) method and also on conduction current. Evaporated Al electrodes suppressed the carrier injection and, as a result, space charge compared with Al plate or SC layer (mechanically contacted electrode). The conduction current also revealed that the carrier injection was suppressed by evaporated Al. The space charge formation and the current showed a significant dependence on not only electrode material but also contact condition between metallic electrode and insulator.