Comparative study between CBD and SILAR methods for deposited TiO2, CdS, and TiO2/CdS core-shell structure

TiO2, CdS, and TiO2/CdS core-shell structures were deposited on fluorine-doped tin oxide (FTO)-coated glass substrate using chemical methods. TiO2 thin films were prepared by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). SILAR was also utilized to deposit CdS film on TiO2 thin film. The structural, surface morphology, and optical characteristics of FTO/TiO2, FTO/CdS, and FTO/TiO2/CdS core- shell structures were evaluated. The FTO/TiO2 films produced by both methods conformed to anatase and rutile phase structures. Corresponding XRD pattern of the FTO/TiO2/CdS sample exhibited one peak corresponding to hexagonal (101) for CdS. Scanning electron micrographs showed nanorod structures for the TiO2 thin films deposited by CBD, contrary to the nanograin structure formed by SILAR. Optical results showed highly extended absorption edge to the visible region for the FTO/TiO2/CdS structure deposited by the two methods. The TiO2 thin films deposited by CBD exhibited higher absorption in the visible region than nanograined TiO2 thin films deposited by SILAR because of the high surface area of the TiO2 nanorod. Photoelectrochemical (PEC) properties of FTO/TiO2, and FTO/TiO2/CdS system were also examined. PEC behavior of FTO/TiO2/CdS was compared with that of FTO/TiO2 deposited by CBD and SILAR. The TiO2 nanorod thin films deposited by CBD showed evidently enhanced PEC performance compared with nanograined TiO2 thin films deposited by SILAR.