Structural,optical and photoconducting properties of sprayed CdSe films

CdSe films were grown by the pyrolytic decomposition of a mixture of aqueous solutions of selenourea (NH₂CSeNH₂) and CdCl₂·5H₂O. The effect of changes in the selenium-to-cadmium ion ratio on the photoconductivity was examined. The as-grown films had low resistance and showed poor photoconductivity gain. When the films were annealed in air the resistance as well as the gain increased appreciably. These changes have been attributed to chemisorption of oxygen. The samples with one part CdCl₂·5H₂O and one part NH₂CSeNH₂ were found to be the most photosensitive, the ratio of dark resistance to light resistance being of the order of 10⁵. The spectral response of the resistance of these films shows a dip in the region of 690 nm, which is in close agreement with the band gap determined from optical absorption measurements.