Effect of Concentrations of Lead Acetate on Structural, Optical and Electrical Properties of Chemically Deposited Nanostructured Films of PbS

Abstract

Thin films of PbS on glass substrates have been prepared by CBD method with lead acetate as the Pb source and thiourea as S source at pH=12. The concentration of lead acetate has been varied from 0.5M to 1.2M at the step of 0.1M. We observed that the crystallite size decreases from 37.43 nm to 19.17 nm and strain increases as the concentration of lead acetate increases from 0.5M to 1.2M. The quantum confinement in the films are evident as the optical band gap increased from 1.4 eV at 0.5M to 2.7 eV at 1.2M. The widths of the midgap states have been signified by the Urbach energy which assumed different values at different molarities. Another effect of this change of concentration of lead acetate is to decrease the electrical conductivity of the films from 1.87x10-3 (Ωcm)-1 at 0.5M to 6x 10-5 (Ωcm)-1 at 1.2M.Although above researchers studied the effect of concentrations of Pb source and/or S source on various properties of the PbS film, they fixed other parameters at their chosen value which are also important as far as the properties of the films are concerned. In this work, we chose a different set of reaction parameters and analysed the effect of concentration of Pb source (lead acetate) on structural, optical and electrical properties of nanostructured PbS thin film prepared by CBD method to observe how grain size, strain, band gap and electrical conductivity follow pattern of change with the concentration of lead acetate.