Single-step synthesis of 3D nanostructured TiO2 as a scattering layer for vertically aligned 1D nanorod photoanodes and their dye-sensitized solar cell properties

In the present investigation we have successfully synthesized 1D vertically aligned rutile TiO2 nanorods (TNR) and 3D TiO2 nanostars (TNS) as a scattering layer by a single step hydrothermal route. The synthesized nanostructures were characterized by X-ray diffraction, scanning-and transmission electron microscopy and X-ray photoelectron spectroscopy. The 1D TiO2 nanorod and 3D TiO2 nanostar samples were further used for N-719 dye sensitized solar cells (DSSC) application. Compared to a nanorod based cell, the photovoltaic performance of the nanostars/nanorods TiO2 cell exhibits excellent DSSC performance, including superior light scattering, rapid electron transport and lower electron recombination rate. The 3D/1D TNS/TNR based DSSC cell exhibits 5.39% power conversion efficiency, which is remarkably higher than that of the bare 1D nanorod based (3.74%) photoelectrode. The detailed interface and transient properties of these nanorod and nanostar based photoanodes in DSSCs were analyzed by electrochemical impedance spectroscopy measurements and open circuit voltage decay measurements in order to understand the critical factors contributing to such high power conversion efficiency. The enhancement of the efficiency for the 3D/1D TNS/TNR photoanode based cell compared to the 1D TNR is mainly attributed to better light scattering capability, faster electron transport and lower electron recombination.