The impact of sodium chloride as dopant on optical and electrical properties of polyvinyl alcohol

Abstract

Solid polymer electrolytes based on polyvinyl alcohol (PVA) complexed with different amounts of sodium chloride (NaCl) (0.1, 0.2, 0.3, 0.4 and 0.5 g) were prepared using solution cast method. The effect of NaCl dopant amount on the optical properties was characterized using UV-Vis spectroscopy. Absorbance spectra, direct and indirect optical band gap energies of PVA/NaCl samples were studied. These band gap energies decreased as NaCl amount in PVA matrix increased. The Urbach energy of samples was also calculated using the Urbach relation which increased significantly as the NaCl amount increased due to the increase in the disorder of the polymer occurred by doping. The electrical conductivity of PVA/NaCl electrolyte samples has been estimated by DC conductivity as function in the NaCl amount at room temperature. DC conductivity of prepared electrolytes containing different amounts of NaCl salt increased from 2.06 × 10⁻² S/m at doped amount 0.1 g of NaCl to 4.60 × 10⁻² S/m at doped amount 0.5 g of NaCl. This increasing was due to the increase in the degree of conjugation of π-orbitals, thus, the increase in the polarons amount in PVA matrix.