Various contributions are distinguished in the experimentally detected dielectric response of organic semiconductor copper phthalocyanine. While a giant dielectric constant of virgin samples is shown to be due to extrinsic effects, the temperature dependence of the intrinsic dielectric constant, being of the order of 10, indicates two structural phase transitions, as well as a dielectric relaxation reflecting the charge carriers’ response. Ac-conductivity data reveal not only the universal dielectric response arising from the polaron tunneling process, but also that another mechanism, which results in the superlinear power law increase in a frequency dependent conductivity, governs the charge transport at lower temperatures.

• Received 4 November 2004

DOI:https://doi.org/10.1103/PhysRevB.71.041202