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

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 H₂ evolution than those from any other conditions.