Controllable and Rapid Synthesis of Long ZnO Nanowire Arrays for Dye-Sensitized Solar Cells

The hydrothermal method is widely used to synthesize ZnO nanowires for electrical and optical devices. However, the rapid synthesis of long vertically aligned ZnO nanowire arrays on a transparent conductive oxide substrate is still a challenge and also time-consuming. In this paper, we report a controllable and rapid growth of long ZnO nanowire arrays by a microwave heating method with fresh precursor solution continuously injected into the reactor. This method can avoid the growth stoppage and keep the concentration of the reactants in dynamic equilibrium during the whole reaction. It is found that the length of the nanowires increases linearly with growth time, and the growth rate is as high as 58-78 nm/min, producing ZnO nanowires with a length over 10 pm after growing for 2-3 h. When these nanowire arrays were used as the photoanodes of dyesensitized solar cells (DSSC), the power conversion efficiency of these ZnO nanowire-based DSSCs increases with the length of the nanowires, which is mainly attributed to the enlarged internal surface area and therefore dye-loading amount enhancement in the longer ZnO nanowires. This controllable and rapid method is useful for synthesizing ZnO or other ultralong 1D nanostructure for nanodevices.