Electrical conductivity and dielectric measurements of CoMTPP

Abstract

Results of X-ray diffraction patterns (XRD) show that the powder of 5,10, 15,20-Tetrakis(4-methoxyphenyl)-21H,23H-porphine cobalt(II) (CoMTPP) has polycrystalline nature with triclinic structure. Miller's indices, (hkl), values for each diffraction peak in XRD spectrum are calculated. The electrical conductivity and dielectric properties of bulk CoMTPP have been investigated in the frequency range 42 Hz–5 MHz and in the temperature range 298–413 K. The frequency dependence of electrical conductivity, σ (ω, Τ), follows the Jonscher's universal dynamic law. The obtained results have been discussed in terms of the correlated barrier hopping (CBH) model, which is well adapted to CoMTPP semiconductor material. Complex impedance data are obtained at different frequency and temperature. The best fitting for the Cole–Cole plots can be represented by an equivalent circuit element composed of RQC. The conductivity in the direct regime, σdc, is described by the variable range hopping (VRH). The values of dielectric constant, ɛ′ (ω), and dielectric loss, ɛ″ (ω), are found to be decrease with increasing frequency due to the interface states capacitance.