ZnO nanowire arrays: Optical scattering and sensitization to solar light

Arrays of ZnO nanowires with different lengths (0.5-2 mu m) and diameters (100-330 nm) were electrodeposited to study the influence of the nanowire dimensions on light scattering. The nanowire length and diameter were found to be major parameters in modifying the intensity and the wavelength of the scattered radiation, respectively. A significant scattering for the whole visible wavelength range was attained in arrays of ZnO nanowires of similar to 1.5 mu m in length and similar to 330 nm in diameter. ZnO nanowire arrays were sensitized to solar light with a conformally deposited thin CdSe layer. A clear correlation between light scattering before coating and absorption in the resulting ZnO/CdSe core-shell nanostructures was found. The enhancement in the scattering for wavelengths where CdSe exhibits a relatively low absorption coefficient resulted in an effective absorption, in the 400-725 nm range of the AM1.5 solar spectrum, as high as 88% with a CdSe shell thickness of similar to 20 nm only.