Effect of gamma-irradiation and doping on the absorption edge and the optical bandgap of silver-doped PVA films

Abstract

Polyvinyl alcohol polymer is doped with silver using sulfonation and gamma radiolysis. Two groups of samples are prepared. In the first group, the samples are prepared at different silver concentrations of 0%, 0.25%, 0.75% and 1%, all at 30 kGy of radiation dose. In the second group, the samples are prepared at 1% of silver doping but under different radiation doses of 20 kGy, 30 kGy, 40 kGy and 50 kGy. The absorption edge and the energy gaps (allowed direct, allowed indirect, forbidden direct and forbidden indirect) are found from the reflectance measurement in the near infrared range. The values show a strong reduction in the energy gap value of about 4 eV compared to pure or silver-doped PVA that is not sulfonated or irradiated. Thus, the suggested fabrication technique associates PVA with the family of low-bandgap polymers. This paves the way for this polymer to serve in technological applications such as infrared sensors, optical light-emitting diodes, field effect transistors, organic photovoltaics and electrochromic devices. The study also covers the absorbance in the mid-infrared range from 400 cm−1 to 4000 cm−1 which gives indication to the types of functional groups existing in this polymer.