Synthesis and characterization of TiO2–ZnO core–shell nanograss hetero-structure and its application in dye-sensitized solar cell (DSSC)

Abstract

TiO2–ZnO core–shell nanograss (NG) hetero-structure comprising of small nanobranches with sharp edge multiple arms was synthesized via two-step synthesis techniques. Liquid phase deposition and dip-coating technique were employed to prepare the TiO2 core and ZnO shell, respectively. The effect of the annealing temperature on the properties of TiO2–ZnO core–shell and the performance of the DSSC has been investigated. The FESEM characterization reveals that at the temperature above 450 °C, NG started to transform into nanoparticle and the particles size increases with temperature. Annealing temperature of 350 °C shows the perfect structure of the TiO2–ZnO NG. The phase transformation from amorphous to wurzite in the TiO2–ZnO core–shell occurs at 350 °C. Above 400 °C, the crystallinity degree of the ZnO shell decreases with the temperature. The optical absorption of the sample increases with temperature up to 450 °C and decreases due to the decrease in the thickness of the sample. The device utilizing the sample annealed at 350 °C performs the best Jsc and η of 1.04 mA cm−2 and 0.204 %, respectively. Annealing temperature of above 350 °C caused the decrease in η and Jsc and it might due to the transformation of NG to nanoparticles and the existence of cracked-structure film.