Photoelectronic properties of (Cu, Fe, Al) incorporated CdS thin films

CdS films, undoped and doped with Al, Cu, and Fe were prepared by the spray pyrolysis technique. The films have a polycrystalline hexagonal structure as shown from their XRD patterns. The crystallinity of pure CdS film is highly distorted by the addition of Al, or Fe, or Cu. The a.c. photoconductivity for the prepared samples was measured. The photoconductivity response spectra show two distinct peaks independent of the incorporated element. The position and intensity of these peaks are affected by the type and concentration of the elements incorporated. The optical absorption coefficient for the samples investigated, as calculated from transmission and reflection spectra, was studied as a function of photon energy. The pure CdS sample shows a sharp absorption edge while the incorporated films show a less sharp curve. The incorporation of Al enhances the d.c. photosensitivity response.