Optical and Electrical Properties of Doped and Undoped Bi<sub>2</sub>S<sub>3</sub>)-PVA Films Prepared by Chemical Drop Method

Abstract

Bismuth sulfide was prepared in PVA matrix by chemical method using solutions of Bi(NO3)3 and Na2S. Bi2S3 was doped during preparation using Br2 vapour and also liquid drops of Br2. Both doped and undoped Bi2S3–PVA films were characterized by SEM, XRF, optical absorption and electrical conductivity measurements. The undoped films consisted of particles of sizes 156 nm-184nm as revealed by SEM micrographs. The films doped with Bromine (Br2) vapour were found to consist of rods of diameters ranging from 75 nm to 80 nm. The films doped with Br2 liquid drops showed rods of diameters ranging from 4843 nm to 6930 nm. XRF spectra confirmed the presence of bismuth, sulfur and bromine in the doped films. The temperature variation of doped and undoped films in the temperature range from 298 K to 383 K shows more or less similar pattern of variation with two regions of conduction. The band gap obtained from the absorption spectra was found to change from 3.61 eV to 3.78 eV and the absorption edge shifted towards the lower wavelength with decrease in diameter of the particles or rods.