Optical properties of ZnS and PEDOT thin films

Wide bandgap Zinc Sulfide ZnS and the conjugated poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) thin films were prepared at room temperature by thermal evaporation for ZnS films and spin coating method for PEDOT thin films. The thicknesses for ZnS films varied from (100, 200, and 300) nm, while it was at 100nm thickness for (PEDOT: PSS) thin film. Zinc Sulfide and PEDOT: PSS films were analyzed using X-ray diffraction, and UV-Visible Spectrophotometry. X-ray diagram revealed that both ZnS and PEDOT: PSS films have polycrystalline structure, ZnS has cubic phase along (111) preferred orientation while PEDOT: PSS has orthorhombic phase along (020) plane. From optical absorption, the results showed that the optical energy gap of zinc sulfide films were 3.0 eV, 3.25 eV and 3.45 eV with increasing thickness from (100-300) nm and the value of the energy gap for the PEDOT: PSS thin film is 3.6eV.