Optical Properties of Sensitized Zinc Oxide Nanorods Electrochemically Prepared

Abstract

The optical properties of bare ZnO nanorods and sensitized nanostructures, with Cu 2 O and CdS, are comparatively studied. These nanostructures may show improved photovoltaic performance compared to planar ones. ZnO nanorod arrays were grown by electrochemical deposition. In a second step, Cu 2 O was also deposited electrochemically, while for CdS successive ion layer adsorption and reaction techniques were used. The experimental results are interpreted using numerical simulation based on an effective medium theory. Bare nanorod samples reveal mainly the direct ultraviolet absorption edge of ZnO (between 3.25 and 3.30 eV) and a monotonically increasing transmittance from the ultraviolet into the red. This increase is originated in light scattering, probably by the nanometric structure of the samples. For the sensitized samples reduced transmittance in the solar spectrum region is observed and several well-defined absorption edges appear. Spectral absorption edge shifts are interpreted comparing with numerical simulations. For CdS the measured shifts are larger than the ones obtained from numerical simulations. The difference may be due to the combined influence of sub-bandgap absorption, light scattering in the nanorod array and quantum confinement in the nanocrystalline structure of sensitizer layers. For Cu 2 O its more complex electronic structure gives larger dispersion in the results although major absorption edges are clearly observed.

Manganese-Doped Zinc Oxide Nanostructures as Potential Scaffold for Photocatalytic and Fluorescence Sensing Applications

“…The red shift in the presence of Mn ions that has been observed in the absorption maxima is attributed to the decrease in the band gap energy, which makes it a better candidate for photocatalytic activities. Analysis of the optical quality of the ZnO nanoparticles is very important due to its wide band gap 3.37 eV and a large exciton binding energy 60 meV, which makes it a unique electronic and photonic semiconducting material [47,48]. The optical activity of Mn-doped ZnO nanostructures was analyzed by using absorption spectra (UV-visible), as shown in Figure 3a.…”

“…In other words, the same material can perform a variety of applications. Furthermore, the high solubility of ZnO [46], wide direct band gap energy of 3.37 eV, and large exciton binding energy of 60 meV [47,48] are properties that show improvements due to the large magnetic moment of the Mn atom. The solution combustion synthesis route was utilized in the present paper, as this is a time and energy-saving single-step facile process for the bulk production of nanoparticles [49,50].…”

Electrodeposition and characterization of composition-graded CdS x Se (1–x) multilayer thin film structures

“…This enhancement is a consequence of an increase in the light scattering in the morphology of the samples. [71,76] For further studying the optical performance of the graded-composition stack samples the E g for each layer was obtained. In order to separate the transmittances of each individual layer from the transmittance of the stack of layers, the transmittance from the previous stack was used as reference.…”

Optical absorption enhancement in sensitized ZnO nanorods for solar cells

“…Eventually Lorentz-Lorenz approximation should be used instead of Bruggeman Eq. (1) [16] but a new parameter related to the porosity should be introduced [23]. Therefore, the choice of the correct solution for the corresponding equation will more complicated [24].…”