Structural, optical and dielectric properties of n-type organic N,N′-dimethyl-3,4,9,10-perylenedicarboximide thin films: effects of annealing

N-type N,N'-Dimethyl-3,4,9,10-perylenedicarboximide ((PTCDI-C1) organic thin films were fabricated by vacuum evaporation procedure. The crystallinity of PTCDI-C1 was analyzed by x-ray diffraction(XRD), while its structure was studied by scan electron microscopy (SEM). The optical properties of as-prepared and annealed PTCDI-C1 thin films were determined by double beam spectrophotometer. The results of XRD and SEM revealed the increase of agglomeration grain size due to thermal effect. The transmittance and reflectance were measured in visible and ultraviolet wavelength spectrum. The normal dispersion of refractive index was modeled according to single oscillator model. For higher energy range (hv > 3.5 eV), the calculated optical conductivity of PTCDI-C1 thin films was observed to increase with increasing of the photon energy. The optical band gap energy of the annealed PTCDI-C1 thin films was found to be decreased as a direct effect of temperature increase. Furthermore, the value of the third nonlinear susceptibility χ (3) values of thin film were lowered as a result of annealing.