Effect of heat treatment on structure, surface morphology, linear and nonlinear optical properties of Na2Pc films for optoelectronic applications

In this paper, we study the influence of thermal annealing on the structural and optical properties of disodium phthalocyanine (Na2Pc) films. Thermal evaporation method under vacuum has been successfully used to deposit thin films of Na2Pc onto quartz and glass substrates. XRD analysis indicated that the pristine film has an amorphous structure and turns into a polycrystalline upon thermal annealing. SEM technique was used to investigate the morphological properties of thin films. The linear and nonlinear optical parameters of pristine and annealed films have been investigated in the wavelength range 200-2500 nm via spectrophotometric mea-surements of T(lambda) and R(lambda). The extinction coefficient of Na2Pc films exhibited four electronic transitions, namely, the Q, N, L and C bands. By applying a single oscillator model, many spectral dispersion parameters have been estimated in the transparent region of the spectrum. The dielectric constants, dissipation factor and optical conductivity were calculated and discussed. The optical transition type, energy gaps and Urbach energy of Na2Pc films were determined by the absorption band edges analysis. Also, the nonlinear refractive index and nonlinear optical susceptibility were evaluated from the linear refractive index results. The results of this investigation indicated the possibility of using Na2Pc films in optoelectronic device applications.