Preparation and Characterization of Submicron Star-Like ZnO as Light Scattering Centers for Combination with ZnO Nanoparticles for Dye-Sensitized Solar Cells

Submicron star-like ZnO (ZnO SZ) was synthesized via a facile hydrothermal method, and a series of composite photoanode materials with different ZnO SZ concentrations in the range from 0 wt.% to 0.20 wt.% were synthesized by a mechanical mixing method. The as-prepared samples were characterized by x-ray diffraction analysis, scanning electron microscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, etc. The results clearly showed that the mean diameter of the ZnO SZ was approximately 300 nm while its length was in the micrometer range, and the ZnO SZ was embedded homogeneously into the ZnO nanoparticle photoanode. Although UV–Vis spectral analysis revealed that increasing the ZnO SZ content decreased the dye adsorption density of the composite photoanode, the photocurrent density–voltage (J–V) characteristic indicated that dye-sensitized solar cells (DSSCs) using the ZnO SZ/ZnO composite photoelectrode exhibited significantly improved photovoltaic performance compared with those using pure ZnO nanoparticles. Electrochemical measurements revealed that DSSCs using 0.10 wt.% ZnO SZ showed improved efficiency of light energy conversion of 1.38%, being 43.75% higher than when using pure ZnO. All these results prove that incorporation of ZnO SZ into the ZnO nanoparticle photoelectrode represents a highly effective method for improving the photovoltaic properties of DSSCs.