Optical properties of multi-layers structured PEO/PVP solid polymer membranes doped with sodium perchlorate

In this present research work, fabrication of multi-layers structured (MLS) polymer membranes has been proposed to understand the variation of the optical bandgap and determine the types of electronic transitions as a function of sodium salt doping concentration1. Solid MLS polymer membranes based on PEO/PVP have been prepared by the well-known solution cast technique. The recorded absorption, transmittance and reflectance spectra revealed that, incident energy absorption increased upon increase of salt dopant concentration and a shift of absorption edge towards lower energy region suggests the good complexation between the host polymers and dissociated salt (Na+, ClO4-) ions, which in turn the energy bandgap decrement expected. A detailed investigation has been carried out on the variation of refractive index of all the MLS polymer membranes as a function of salt doping concentration. The miscibility between the sodium salt and the individual polymers present in MLS polymer membranes can be understood from the linear relationship between the refractive index and the volume fraction of the added salt. The increase of extinction coefficient at high wavelengths was observed. The optical band gap measured from the plots of (ahu)x versus photon energy (hu) was compared to that determined from the optical dielectric loss. The Urbach energy was found to vary with as a function of sodium salt concentration.