Controllable electrochemical synthesis of ZnO nanorod arrays on flexible ITO/PET substrate and their structural and optical properties

The structural and optical properties of vertically aligned zinc oxide (ZnO) nanorod arrays (NRAs) which were grown on the flexible indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrate (i.e., ITO/PET substrate) with a thin sputtered ZnO seed layer via the electrochemical deposition method were studied. By changing the applied voltage and zinc nitrate concentration, the height/width and density of ZnO NRAs were controlled, with investigation on their crystallinity and optical properties. To understand the effect of ZnO seed layer on the growth property of ZnO nanorods, they were also grown on ITO/PET without any seed layer. Under an applied cathodic voltage of −2 V and zinc nitrate concentration of 10 mM, the ZnO NRAs increased the total transmittance up to 88.7% in the visible wavelength region due to the antireflective property and their X-ray diffraction (0 0 2) peak intensity was largely enhanced. Additionally, the near band edge emission of ZnO was significantly enhanced in photoluminescence spectrum. The light scattering and surface wetting properties were also explored.

Highlights► Vertically aligned ZnO nanorod arrays were grown on flexible transparent substrate by the electrodeposition. ► Morphology and optical properties were controlled by varying the deposition voltage and the concentration of growth solution. ► Crystallinity and photoluminescence were studied under different growth conditions. ► Well aligned ZnO nanorod arrays show the good antireflection and wetting properties. ► Optimized ZnO nanorod arrays exhibit an increased diffuse light scattering with keeping high transparency.