Dielectric Properties and AC Conductivity of Organic Films of Copper(II) 2,9,16,23-Tetra-tert-butyl-29H,31H-phthalocyanine

Abstract

Copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuTTBPc) thin films have been obtained using a physical vapor deposition technique. X-ray diffraction analysis confirmed their amorphous nature. The dielectric constant and electrical conductivity were measured over the frequency range from 50 Hz to 8 MHz and temperature range from 293 K to 393 K. The dependence of the dielectric relaxation spectra on frequency at different temperatures was measured and discussed. In addition, the spectral dynamics of both the real and imaginary parts of the complex electric modulus over a wide temperature range is explained. The activation energy of the relaxation process (ΔEM) was estimated to be 0.26 eV. Moreover, the dependence of the alternating current conductivity on both temperature and frequency was investigated. Additionally, the exponent (s) of the power law of conductivity versus temperature confirmed that the correlated barrier hopping (CBH) model is a successful and appropriate mechanism to explain the charge transportation inside CuTTBPc films. According to this model, the density of localized states N(EF) at room temperature and frequency of 500 kHz was evaluated to be 4.11 × 1023 eV−1 cm−3. This high density of electron states indicates that CuTTBPc can be recommended as a candidate material for use in solar cells.