**3.1 Nanowires**

Nanowires (**Figure 2**) are one-dimensional nanostructure in cylindrical form. They have lengths in the range of a few micrometers to centimeters and their diameters are in the nanometer range. L. Li et al. [4] have demonstrate that the ITO nanowires coated by TiO2 have grown by a thermal evaporation method. The high annealing temperatures between 350 and 600°C increase the crystallinity of TiO2 shell and suppress electron recombination in the core-shell nanostructures. The tin-doped indium oxide (ITO)-TiO2 core-shell nanostructures are tested as the photoanode for DSSCs. The vertically aligned nanowires are expected to efficiently transport electrons to the substrate where the current is collected. These nanowires have high density, which enables high dye loading and high current density during device operation. The open-circuit voltage decay (OCVD) measurements of (ITO)-TiO2 core-shell nanostructures show that the electron lifetime increases by quantity of HfO2 magnitude insertion. ITO-TiO2 core-shell nanostructures with HfO2 blocking layers are promising photoanodes for DSSCs.
