Bi-layer of nanorods and three-dimensional hierarchical structure of TiO 2 for high efficiency dye-sensitized solar cells

A novel bi-layer structure assembled by nanorods and three-dimensional hierarchical TiO 2 is synthesized by a facile two step hydrothermal method. By adjusting the acid concentration, the morphology of three-dimensional hierarchical TiO 2 can be well controlled. This bi-layer structure combines the merits of one-dimensional nanorods which can serve as direct electrons transport pathways and three-dimensional hierarchical structure supplying light scattering ability and large specific surface area for dye loading. Hence, the photovoltaic performance of the dye-sensitized solar cells based on the bi-layer TiO 2 is greatly enhanced compared to that of single nanorods film. The maximum short-circuit current and power conversion efficiency of the DSSCs based on bi-layer TiO 2 structure reach 12.55 mA/cm 2 and 5.61% respectively, which are remarkably larger than those of 5.00 mA/cm 2 and 2.38% for the DSSC based on a single layer TiO 2 nanorods film. The superior performance of bi-layer TiO 2 structure is attributed to the large dye loading amount and light scattering properties due to the unique hierarchical structure.