Electrical and optical properties of pure and silver nitrate-doped polyvinyl alcohol films

The electrical conductivity, current-voltage (I-V) characteristics and optical absorption of pure and AgNO3-doped polyvinyl alcohol (PVA) films have been studied under different conditions. The electrical conductivity increased with increasing dopant concentration up to 0.5 wt.% of the dopant and then showed a decrease beyond this concentration. The increase in conductivity for dopant concentration up to 0.5 wt.% is attributed to formation of charge transfer complexes while the decrease for concentrations above 0.5 wt.% may be due to segregation. The variation of electrical conductivity with temperature showed two regions of activation with activation energies 0.8 and 0.3 eV for undoped films and 1.3 and 0.3 eV for doped films. I-V characteristics indicated that Schottky emission is the dominant charge transport mechanism in both undoped and AgNO3-doped films. Optical absorption studies in the wavelength range 190-600 mn showed additional peaks in the wavelength region 391-417 nm for differently doped films, in addition to the peak at 273 nm for undoped PVA. The optical energy gaps and band edge values shifted to lower energies on doping up to a dopant concentration of 0.5 wt.% but showed an increasing tendency for further increase in dopant concentration. (C) 2002 Elsevier Science B.V. All rights reserved.