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

Abstract

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 1020 molecules per cm3. Temperature-dependent analysis indicated that at 296 K all O2 molecules, and roughly one half of the H2O molecules, were mobilized and diffused with diffusion coefficients DO2 of 3 ∗ 10−8 cm2/s and DH2O of 1.3 ∗ 10−10 cm2/s. Electrical analysis of ZnPc layers in controlled atmospheres revealed that the electrical properties of the bulk were determined by O2, whereas H2O influences the surface conductivity. A space-charge density of (1.6 ± 0.2) ∗ 1016 O2− ions per cm3 was measured in atmospheric conditions.