Optical absorption and dispersion analysis based on single-oscillator model of polypyrrole (PPy) thin film

In this work, polypyrrole samples were synthesized by chemical oxidative polymerization technique with Iron (III) chloride as an oxidant. Thin films of PPy were prepared by spin coating technique. The molecular structure of polypyrrole film was characterized by Fourier transform infrared spectroscopy (FTIR). The optical properties of the PPy films were studied using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The recorded absorption measurements in the UV–vis region show two well defined absorption bands. The analysis of the spectral behavior of the absorption coefficient (α), in the absorption region revealed two direct transitions. The dispersion parameters were determined and discussed based on the single oscillator model. According to the analysis of dispersion curves, the parameters, namely; dispersion energy (Ed), oscillator energy (Eo), high frequency dielectric constant (ɛ∞) and lattice dielectric constant (ɛL) were evaluated. Discussion of the obtained results and their comparison with the previous published data were also given.

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► Characterization of PPy shows successful incorporation of the molecular structure.
► The recorded absorption spectrum of PPy film shows two absorption bands.
► Two direct allowed transitions were observed with band gaps of 1.60 and 2.22 eV.
► The dispersion parameters were discussed based on the single oscillator model.