Synthesis and characterization of TiO_2-ZnO core-shell nanograss hetero-structure and its application in dye-sensitized solar cell (DSSC)

摘要

TiO_2-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 TiO_2 core and ZnO shell, respectively. The effect of the annealing temperature on the properties of TiO_2-ZnO core-shell and the performance of the DSSC has been investigated. The FESEM characterization reveals that at the temperature above 450 ℃, NG started to transform into nanoparticle and the particles size increases with temperature. Annealing temperature of 350 ℃ shows the perfect structure of the TiO_2-ZnO NG. The phase transformation from amorphous to wurzite in the TiO_2-ZnO core-shell occurs at 350 ℃. Above 400 ℃, the crystallinity degree of the ZnO shell decreases with the temperature. The optical absorption of the sample increases with temperature up to 450 ℃ and decreases due to the decrease in the thickness of the sample. The device utilizing the sample annealed at 350 ℃ performs the best J_(SC) and η of 1.04 mA cm~(-2) and 0.204 %, respectively. Annealing temperature of above 350 ℃ caused the decrease in η and J_(SC) and it might due to the transformation of NG to nanoparticles and the existence of cracked-structure film.