Refractive index, optical bandgap and oscillator parameters of organic films deposited by vacuum evaporation technique

In this work, the organic thin films of 8-hydroxyquinoline aluminum (Alq3), 9,10-bis-(β-naphthyl)-anthrene (ADN), and aluminum (III) bis-(2-methyl-8-quninolinato)-4-phenylphenolate (BAlq) were deposited by vacuum evaporation technique, and the optical and dielectric properties of the films were investigated. The optical constants such as refractive index, extinction coefficient, dielectric constant and dissipation factor were determined from the measured transmittance spectra using the envelope method. Meanwhile, the dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple–DiDomenico (W–D) model, and the physical parameters of the average oscillator strength, average oscillator wavelength, average oscillator energy, the refractive index dispersion parameter and the dispersion energy were achieved. Furthermore, the optical bandgap values were calculated by W–D model and Tauc model, respectively, and the values obtained from W–D model are in agreement with those determined from the Tauc model. These results provide some useful references for the potential application of the thin films in optoelectronic devices.