Hierarchical ZnO architectures consisting of nanorods and nanosheets prepared via a solution route for photovoltaic enhancement in dye-sensitized solar cells

Abstract

ZnO nanorod–nanosheet (NR–NS) hierarchical architectures grown on fluorine-doped tin oxide (FTO) coated glass substrates were prepared via a two-step solution route, which involved the growth of the ZnO nanorods on the FTO substrate, followed by a secondary growth of the ZnO nanosheet on the as-grown backbone. The characterization showed that the nanosheets composed of very small nanoparticles underwent oriented attachment by closely covering the nanorods, resulting in an enhancement of the internal surface area. The ZnO nanostructure films were applied to dye-sensitized solar cells (DSSCs). The photovoltaic results demonstrated that the short circuit current density and the energy conversion efficiency of the NR–NS hierarchical architecture DSSCs were 4.806 mA cm⁻² and 1.13%, respectively, which was almost two times higher than those of nanorod only arrays. The dye desorption result and diffused reflectance spectra indicated that the dye absorption amount and light scattering within the NR–NS hierarchical architecture photoanode were higher than those for the nanorod photoanode. The significant improvement was a consequence of the enhancement of dye loading and light scattering within the NR–NS hierarchical architecture photoanode.