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 H 2 O molecules, were mobilized and diffused with diffusion coefficients D O 2 of 3 ∗ 10 −8 cm 2 /s and D H 2 O 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 H 2 O 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.