Quantification and effects of molecular oxygen and water in zinc phthalocyanine layers

Gas effusion measurements on zinc phthalocyanine (ZnPc) layers showed the presence of a significant amount of oxygen and water inside the material during exposure to ambient conditions. Of both species the bulk concentration lay in the range of 10(20) molecules per cm(3). Temperature-dependent analysis indicated that at 296 K all O-2 molecules, and roughly one half of the H2O molecules, were mobilized and diffused with diffusion coefficients D-O2 of 3 * 10(-8) cm(2)/s and D-H2O of 1.3 * 10(-10) cm(2)/s. Electrical analysis of ZnPc layers in controlled atmospheres revealed that the electrical properties of the bulk were determined by O-2, whereas H2O influences the surface conductivity. A space-charge density of (1.6 +/- 0.2) * 10(16) O-2(-) ions per cm(3) was measured in atmospheric conditions.