Blue shift of band gap for vanadyl 2,3-naphthalocyanine (VONc) thin films monitored at thermal effect

Abstract

Thermally evaporated films of promised vanadyl 2,3-naphthalocyanine (VONc) materials were prepared. Both structural and optical properties of VONc films were monitored before and after annealing at different annealing temperatures of 423, 473 and 523 K. The structural properties were investigated by x-ray diffraction and scanning electron microscopy which showed an agglomerated grains under annealing effect. The transmittance and reflectance of the VONc films were detected as a function of wavelength in the range 200–2500 nm at those annealing temperatures. Linear and nonlinear optical properties of these films were studied under thermal effect. Varies interesting optical investigations were observed for these VONc films which develop their optoelectronic applications. A blue shift of the optical band gap of the investigated films with annealing temperatures is observed. Two different energy gaps appear in the range of 1.25–1.5 eV, and at the range of 2.5–2.75 eV. The third-order nonlinear optical susceptibility showed a decreasing dependence with the annealing temperatures due to its local field. Three promising maximum optical conductivity energies were observed.