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 hig
hly distorted by the addition of Al, or Fe, or Cu. The a.c. photoconductivi
ty for the prepared samples was measured. The photoconductivity response sp
ectra show two distinct peaks independent of the incorporated element. The
position and intensity of these peaks are affected by the type and concentr
ation of the elements incorporated. The optical absorption coefficient for
the samples investigated, as calculated from transmission and reflection sp
ectra, was studied as a function of photon energy. The pure CdS sample show
s a sharp absorption edge while the incorporated films show a less sharp cu
rve. The incorporation of Al enhances the d.c. photosensitivity response.