Comparison of ZnS thin films deposited by chemical bath using different precursor solutions

Zinc sulfide thin films were prepared on fluorine doped tin oxide glass, using different precursor solutions in order to determine the best process for obtaining ZnS films that may replace CdS layers in solar cells. Urea was used as a complexing agent, and thiourea and thioacetamide were used as sulfur precursors. The films have high transmittance, an energy band gap around 3.5 eV and good Zn/S ratio (around 1). X-Ray measurements show that the best crystallinity and stoichiometry in the films are obtained when pre-heated thioacetamide is used as the S precursor. The films crystallize in the cubic phase with grain sizes in the range from 12 to 15 nanometers. All these properties make these films a good choice for CdS replacement in CdTe and CuInGaSe2 solar cells.