Facile growth of ZnO nanowire arrays and nanoneedle arrays with flower structure on ZnO-TiO2 seed layer for DSSC applications

In this present investigation, zinc oxide-titanium oxide (ZnO-TiO 2 ) thin films were prepared by sol-gel spin coating technique and used as a blocking as well as seed layer, and followed by, ZnO nanowire arrays (NWAs) and nanoneedle arrays (NNAs) were synthesized on ZnO-TiO 2 seed layer by facile hydrothermal technique by varying some parameters such as solution concentration, growth time and growth temperature. They are used as a photoanode for dye sensitized solar cell (DSSC) and characterized by spectroscopic and microscopic technique to investigate about the crystal structure, morphology and optical properties. The presence of hexagonal wurtzite structure of the prepared nanostructures grown along with (002) plane was confirmed by using X-ray diffraction (XRD), Raman spectra and transmittance electron microscope (TEM). NWAs and NNAs were observed with flower like structure consisting of nanowires and nanoneedles, respectively by field emission scanning electron microscope (FE-SEM). UV–Vis spectra imply that NNAs have a better light absorbance with more dye loading than NWAs. It could be found from current density-voltage (J-V) curve that the photovoltaic conversion efficiency of the NWAs and NNAs based DSSC is 0.91% and 1.47%, respectively. Electrochemical impedance spectroscopy (EIS) shows that DSSC based on NNAs photoanode has a better electron lifetime with less electron recombination than DSSC based on NWAs photoanode.