A general guide for adsorption of cadmium sulfide (CdS) quantum dots by successive ionic layer adsorption and reaction (SILAR) for efficient CdS-sensitized photoelectrochemical cells

Abstract

Using CdS quantum dots grown on the surface of mesoscopic TiO2 film through SILAR deposition as a model semiconductor-sensitizer, common but not well understood parameters in the deposition process such as precursor compound & its concentration, solvent, and dipping time of the substrate electrode are systematically checked for suggesting a general guideline to make efficient CdS-sensitized mesoporous TiO2 electrode for photovoltaic and photocatalytic applications. Among many variables, the electrostatic interaction between intrinsic (+)-charge of metal cation (Cd2+) and induced (-)-charge of TiO2 surface, which is generated by the degree of solution's pH above the point of zero charge (pzc) of TiO2, is observed to be the most critical for controlling the extent of CdS adsorption by taking absorbance and TEM images after a defined SILAR process. The acetate salt is the best one for faster and more adsorption of as-grown CdS due to its role of increasing the pH value in solution as a weak base. The highest pH of ~ 9.5 obtained by adding a weak base, triethanolamine (TEA) to any Cd2+-dissolved solution induces the most adsorption of CdS within the least cycle optimized for better photovoltaic conversions efficiency and photoelectrochemical H-2 evolution than those from any other conditions.