Electrical and optical properties of vacuum deposited ZnPc and CoPc thin films and application of variable range hopping model

Sandwich and planar structures have been fabricated using zinc phthalocyanine (ZnPc) and cobalt phthalocyanine as active layers and gold (An) as electrodes by thermal evaporation method. The permittivity epsilon is determined from the dependence of capacitance on film thickness. J-V characteristics of Au/ZnPc/Au and Au/CoPc/Au structures at room temperature have been performed. Thermally generated hole concentration p(0), hole mobility mu(p), total trap concentration N-t and depth of the trap level have been estimated. The activation energies of the films have been determined from the Arrhenious plots of In sigma versus 1000/T. Employing the variable range hopping model, hopping conduction parameters have been calculated. The absorption and reflectance spectra of ZnPc and Cope thin films deposited at room temperature have been recorded in the spectral range 300-900 nm. The optical band gaps of the films have been determined from the alpha(2) versus hv graph. The optical constants n and k have been found. The real and imaginary parts of the optical dielectric constant epsilon(1) and epsilon(2) have been calculated.