Direct current conductivity and thermally stimulated current of β-nickel phthalocyanine films using gold and aluminium electrodes

Abstract

Current density-voltage characteristics and thermally stimulated currents have been obtained from thin films of β-nickel phthalocyanine particles dispersed in a polymer binder, when sandwiched between ohmic gold and blocking aluminium electrodes. At low voltages, the current in the forward direction varies exponentially with voltage. At higher voltages, two separate regions of space-charge limited current conduction under forward bias were observed. Under reverse bias, the conduction process at low voltages is determined by Schottky emission over a potential barrier of approximate height, 0·89 eV and thickness 65 nm. At higher voltages, the Poole-Frenkel effect was observed. The activation energy of the hole trapping level determined from the thermally stimulated current measurements has an electric field dependence. The results are interpreted in terms of the Poole-Frenkel effect.