Cu:ZnS and Al:ZnS thin films prepared on FTO substrate by nebulized spray pyrolysis technique

Cu doped ZnS and Al doped ZnS thin films were coated on the fluorine-doped tin oxide substrates by nebulized spray pyrolysis technique. The structural, morphological, optical and electrical properties of Cu and Al doped ZnS thin films were investigated. X-ray diffraction analysis revealed that all the doped ZnS films are polycrystalline nature with hexagonal structure. The size of the crystallites was also determined. Field emission scanning microscopic images of the doped ZnS thin films shows smooth and uniform plaque shaped grains on to the surface of the films. Energy dispersive analysis of X-ray confirms the presence of expected elements without any other impurities and nature of the thin film. The optical transmittance values were observed to be 71 and 74% for Cu:ZnS and Al:ZnS films, respectively. The observed high band gap value is 3.67 eV for 2% Cu:ZnS film. The room temperature photoluminescence spectra of the Cu:ZnS films showed blue emission peaks at wavelength 407 and 422 nm. The visible emission band at 478 nm is due to the recombination of electrons in the sulphur vacancy level and holes in the zinc vacancy. Low resistivity value was observed at 4% Cu:ZnS film is explained by crystalline size and carrier concentration. The enhanced electrical properties behavior of Cu and Al doped ZnS thins film proposes for effective solar cell application.