Influence of Mn-doping with CdS on the structural and optical properties of ZnS/CdS/TiO2 photoanodes

In the present work, Mn-doped semiconductor sensitized photoanodes were prepared by spin coating followed by successive ionic layer adsorption and reaction method. The structure and morphology of Mn-doped anodes were investigated by XRD, Raman, SEM with EDX and TEManalysis. These analyses depict the enabled presence of CdS nanoparticles into the nanoporous TiO2 structure. The calculated crystallite size of Mn-doped CdS nanocrystals is found to be 2 nm from XRD pattern. The optical absorption results reveal that Mn-doping with CdS could greatly enhance the absorption of TiO2 in the visible region, leading to a decrease in the bandgap energy from 3.43 to 2.02 eV. Photoluminescence (PL) spectrum shows two strong emission peaks one at near UV (367 nm) and the other at violet region (411 nm) with an additional low intensity red emission peak at 633 nm due to oxygen vacancies and defects. On comparing with undoped CdS film, PL spectra suggest that all the emission peaks are slightly blue shifted for the Mn-doped film (ZnS/Mn-CdS/TiO2). It has been demonstrated that the doping of Mn with CdS on the surface of the TiO2 nanostructured film could improve the electrical performance of the anode through rapid electron transport by enhanced absorption of the incident light.