Influence of pH on electrochemically deposited CdSe thin films

Polycrystalline CdSe thin films have been electrodeposited at room temperature on stainless steel (ss) and fluorine doped tin oxide (FTO) coated glass substrate from aqueous electrolytes containing salts of cadmium acetate and selenium dioxide. The pH of the bath is varied from 1.75, at the interval of 0.25, to 3. The effect of pH on the photoelectrochemical (PEC), structural and optical properties of the deposited film is studied. The pH of the bath is optimized by the PEC technique and is observed to be 2.75. The analysis of the XRD patterns show that the deposited CdSe material is polycrystalline with a hexagonal crystal structure. SEM study shows that the total substrate surface is well covered by uniformly distributed spherical shaped grains. The optical absorption studies reveal that the pH of the electrolytic solution has a significant effect on the band gap of the CdSe thin film. The transition involved is direct with band gap energy Eg of 1.72 eV.