Influence of thermal and plasma treatments on the electrical properties of poly(para-phenylene vinylene)-based diodes

We have studied the influence of plasma and thermal treatments on the electrical properties of poly(para-phenylene vinylene) (PPV) thin films in metal-polymer-metal structures. Thermal heating of the samples modifies the diode characteristic by reducing the voltage threshold and by favouring the formation of the rectifying contact at the bottom side. Plasma treatments with oxygen or nitrogen drastically change the conductivity of the polymer with disappearance of the rectifying behaviour and increase the current by many orders of magnitude. Attempts to explain the modifications of the electrical property of the treated samples are given, using previous results from X-ray photoelectron spectroscopy (XPS) which highlight the role of the interfacial layer formed by chemical reaction between the polymer and metallic electrode.