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Oxygen induced charge carrier generation and trapping in vacuum deposited phthalocyanine thin films

I. ZHIVKOV1,*

Affiliation

  1. Central laboratory of photoprocesses “Akad. J. Malinowski”, Bulgarian Academy of Sciences, Akad. G. Bonchev Str. bl. 109, Sofia, Bulgaria

Abstract

Investigations of the temperature dependencies of the electrical conductivity and thermo-modulated space charge limited current spectroscopy measurements are carried out on metal-free phthalocyanine (H 2Pc) thin films, in a gap sample configuration with interdigital gold electrodes in a controlled atmosphere. It was found that the influence of O 2 on the dark conductivity of H 2Pc films is a thermally activated process at 360 K. The H2Pc-O 2 interaction is a two-stage process characterized by an activation energy (Ea)=0.36 eV of creation and E a=0.60 eV of decay of charge transfer complexes and subsequent generation of free charge carriers, increasing the Ohmic current. The dependence of the Ohmic current on the O 2 concentration (for small O 2 concentrations) is linear. An increased concentration of traps, as a result of the oxygen influence upon a trap level of 0.52 eV depth, was observed..

Keywords

Phthalocyanines, Gas sensors, Density-of-states, Thermo-modulated space-charge-limited current spectroscopy.

Submitted at: Nov. 5, 2008
Accepted at: Oct. 3, 2009

Citation

I. ZHIVKOV, Oxygen induced charge carrier generation and trapping in vacuum deposited phthalocyanine thin films, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 10, pp. 1396-1399 (2009)