CHEMICAL-DEPOSITION OF PHOTOSENSITIVE CDS THIN-FILMS ON POLYESTER FOILS

Cadmium sulfide thin films were deposited on polyester foils (PE) by chemical bath deposition using triethanolamine (TEA) and citrate (Citrate) as ligand for complexation with cadmium ions. X-ray diffraction (XRD) analyses show that the CdS films deposited by the TEA method possess hawleyite (cubic) structure, but crystallinity is not noticeable in the films deposited by the Citrate method. An overgrowth of possible organometallic matter on the CdS films is common to the films deposited by the TEA method on polyester as well as glass substrates. The results of Fourier transform infrared (FTIR) spectroscopy with attenuated total reflectance (ATR) mode as well as XRD analyses indicate no organic impurities in the CdS films obtained by the Citrate method. These films are also smooth, as seen in optical micrographs. The optical transmittance spectra indicate that the films obtained by the Citrate method possess an optical band gap in the range of 2.55-2.6 eV. The films are very photosensitive, offering photocurrent to dark current ratios of > 10(7) under 600 Wm(-2) tungsten-halogen illumination. The films could be converted into n-type (resistivity, 1 Omega . cm) by immersing the films in 0.05M HgCl2 solution for 20 min followed by air annealing for 30 min.