A Facile Approach to Construct Multiple Structured ZnO Crystals by Trisodium Citrate-Assisted Hydrothermal Growth Toward Performance Enhancement of Dye-Sensitized Solar Cells

ZnO crystals with different morphologies including microrods, hierarchical microspheres, and hollow microspheres were fabricated via a simple and low-cost trisodium citrate-assisted hydrothermal method. The related morphologies and structures of the as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that trisodium citrate played a crucial role as a capping agent in the formation of ZnO nanostructures, and accordingly, the rational growth mechanism was proposed. The obtained ZnO nanostructures were used as a photoanode in dye-sensitized solar cells (DSSC), and the photovoltaic results demonstrated that the short circuit current density and the overall conversion efficiency of the hierarchical microspheres based DSSC were 6.05 mA cm–2 and 1.42%, respectively, which were largely improved compared with those of the microrods based DSSC (1.92 mA cm–2 and 0.41%) and hollow microspheres based DSSC (3.37 mA cm–2 and 0.79%). The significant improvement for the former was attributed to the sufficient dye loading and efficient light scattering.