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.

Morphology, Optical and AC Electrical Properties of Copper Phthalocyanine Thin Films

“…The coordination of O 2 to MPc at the airPc interface results in the formation of MPc + and O − 2 and causes the injection of hole charge carriers into the solid [26] and hole concentration near the surface increases. Thus a rise in electrical conductivity is achieved through a doping mechanism [27] at low frequency region.…”

A Mossbauer Study of the Low Spin-High Spin Transition of an Oxygen Adduct Formed in Solid β -Fe(II)Phthalocyanine

“…We attributed the spectral changes at low temperature to coordinate with a freely floating O 2 molecule in the sixth axial position of a five-coordinate μ-oxo bridged or μ-peroxo bridged Fe III Pc. Such free O 2 molecules have been reported for Pb II Pc and Zn II Pc [4,5,13]. We assumed that the bonding with O 2 , was weak due to constraints imposed in the solid matrix and that the bond ruptured at higher temperatures.…”

Atomic Imaging of the Irreversible Sensing Mechanism of NO2 Adsorption on Copper Phthalocyanine

“…1,18−20 The induced p-type conductivity of MPc films has been modeled as formation of charge transfer complexes on the metal centers with oxidative dopants. Weak oxidative analytes (such as O 2 ) 4, 19 chemisorb weakly on MPc films as electron acceptors and form superoxide adducts consisting of oxidized MPc + and O 2− species; holes are injected into the bulk solid from the positively charged MPc + . The injection of these holes moves the valence band (HOMO) edge toward the Fermi level, forming a p-type MPc film.…”