Optical band gap of polyvinylpyrrolidone/polyacrilamide blend thin films

Abstract

Thin films of polyvinylpyrrolidone, polyacrilamide and their blends were prepared using solution cast method and characterized using X-ray diffraction (XRD) technique. Optical absorption spectra of these thin films have been recorded in the wavelength range 190-600 nm using UV-visible spectrophotometer. Optical band gap of the films has been calculated by using Tauc’s relation and variations in the values of optical band gap with the variation of composition in the blend films have been found from 4.77 to 5.10 eV. The tail width of the localized states has been calculated by using Urbach’s relation. Absorption coefficient and extinction coefficient have been calculated at 220 nm wavelength in the region where the absorbance by the thin film is the maximum. The optical band gap has been correlated with the number of carbon atoms per molecule.