The influence of oxygen on lead phthalocyanine thin films

The dark electrical behaviour of oxygen-exposed thin films of monoclinic lead phthalocyanine (PbPc) with gold electrodes was studied for both planar and sandwich devices. Slow but steady increase of conductivity was observed for the planar devices subject to an oxygen flow at atmospheric pressure, with no saturation within 48 h. The current passing through the devices was found to be remarkably dependent on thickness. The sandwich devices (Au-PbPc-Au) with an oxygen-doped phthalocyanine layer exhibited a rectifying effect for exposure times less than 2 h, remaining after sequential annealing under vacuum at 423 K for 48 h. The behaviour is discussed as a Schottky-type barrier and its width and height are estimated.