Wet-chemical route to ZnO nanowire-layered basic zinc acetate/ZnO nanoparticle composite film

ZnO nanowire-layered basic zinc acetate (LBZA)/ZnO nanoparticle (NP) composite films with different NP occupying extents have been synthesized using a simple wet-chemical route, i.e., aligned ZnO nanowire (NW) array first formed by an aqueous chemical bath deposition (CBD) and then heterogeneous nucleation and growth of LBZA/ZnO NPs on the surface of ZnO NWs by another base-free CBD. The features of the composites from three-dimensional (3D) NW-nanosheet (NS) networks to dense NW-NP composite films and NW-NP composite films with flowerlike particles are able to be obtained easily by varying the NP growth period. X-ray diffraction (XRD) and cathodoluminescence (CL) analyses indicate that the LBZA fraction and defect concentration in the composite film are increased with the NP growth period in the base-free chemical bath solution. Shifts of the ZnO (002) diffraction peak and UV emission peak with the NP growth period are observed at the series of composite films. HRTEM analyses indicate that there is no epitaxial relationship between the ZnO NW and ZnO NPs, suggesting that heterogeneous nucleation of LBZA structure on the surface of the ZnO NWs is crucial for the formation of the NW-NP composite using the base-free route. Photovoltaic measurements of the ZnO NW-LBZA/ZnO NP composite dye-sensitized solar cells (DSSCs) show that the overall efficiency is affected by the LBZA fraction, defect concentration, and cracks within the NW-NP composite film.