In this work a double-layer photoanode composed of TiO2 nanocrystals (NCs) and hollow spheres (HSs) was applied in CdS:Mn sensitized solar cells. TiO2 NCs with dominant size of 25 nm were synthesized by a facile hydrothermal method. TiO2 HSs were also prepared through the liquid phase deposition (LPD) of TiO2 on carbon spheres followed by a calcination process. The double electron transport layer of quantum dot sensitized solar cells (QDSCs) was formed of a nanocrystalline TiO2 layer covered by a light scattering HSs film. The corresponding thicknesses were also controlled to be about 10 µm and 7 µm, respectively. The sensitization of photoanode with Mn doped CdS NCs were carried out by a successive ionic layer adsorption and reaction (SILAR) technique. The apparent Mn/(Mn+Cd) molar ratio was altered in a wide range of 0-9%. The corresponding QDSCs were fabricated and the doping process was optimized for the improved power conversion efficiencies. According to the results, the QDSCs with a double-layer photoanode sensitized with Mn/(Mn+Cd) ratio of 7.0% showed the maximum efficiency of 3.26%. This value was increased about 61% and 18% compared to those of the reference cells with single nanocrystalline and double-layer photoanodes sensitized with un-doped CdS NCs. The reason was addressed due to the Mn related electron energy states within the bandgap energy of CdS NCs and improved electron transport inside the cells.
