Structural, optical and electrical properties of sulphide based heterojunction thin film

This contribution presents structural, optical and electrical properties of PbS/CdS thin films at different annealing temperatures. The XRD analysis reveal the existence of three different crystalline phases, i.e., the beta-CdS, hawleyite-CdS and greenockite-alpha-CdS phases within the CdS-shell of PbS/CdS core shell thin film. The dislocation density and microstrain decreased with annealing temperatures indicating a decrease in lattice imperfections and formation of high quality film and it can be attributed to the increase in grain size of the film with increase in annealing temperatures. Optical studies placed the band gaps at 1.25eV-1.75eV. About the same magnitude were found from electrical conductivity test. The samples exhibited high conductivity with increasing annealing temperatures which resulted to the bumping of electrons from the valence band to the conduction band. The high absorbance suggest that the film could be coated on collectors to enhance solar energy collection. The achieved band gaps placed the PbS/CdS fabricated with the presented method as a good material for solar photovoltaic applications.