Abstract
The AC-electronic and dielectric properties of different phthalocyanine films (ZnPc, CuPc, FePc, and H2Pc) were investigated over a wide range of temperature. Both real and imaginary parts of the dielectric constant (∊ = ∊1 − i∊2) were found to be influenced by temperature and frequency. Qualitatively the behavior was the same for those compounds; however, the central atom, film thickness, and the electrode type play an important role in the variation of their values.
The relaxation time, τ, was strongly frequency-dependent at all temperatures and low frequencies, while a weak dependency is observed at higher frequencies. The relaxation activation energy was derived from the slopes of the fitted lines of ln τ and the reciprocal of the temperature (1/T). The values of the activation energy were accounted for the hopping process at low temperatures, while a thermally activated conduction process was dominant at higher temperatures.
The maximum barrier height, Wm, was found to be temperature and frequency dependent for all phthalocyanine compounds. The value Wm depends greatly on the nature of the central atom and electrode material type. The correlated barrier hopping model was found to be the appropriate mechanism to describe the charge carrier's transport in phthalocyanine films.