Dietmar Leinen

CuS and ZrO ₂ /CuS thin films have been deposited at 200 °C in ambient atmosphere by spray pyrolysis onto stainless steel S304 and aluminum AA1050 sheets in order to be used as prospective solar absorbers for thermal energy harvesting. Zirconia has been deposited as a top layer working as an antireflection coating increasing the solar absorption and protecting the underlying copper sulfide layer, which works as the solar light absorbing material. Solar selectivity of the samples was evaluated measuring the total hemispherical reflectivity in the ultraviolet‐visible infrared range and calculating solar absorptance and thermal emittance. The solar selectivity was optimized by tuning the film thickness of the coating stack. X‐ray diffraction, SEM and X‐ray photoelectron spectroscopy analyses have been used to proof crystal phase, coverage, film thickness, and surface contamination of optimized samples, revealing that the copper sulfide film is CuS covellite and the optimized film thicknesses are in the range of 50 nm for the ZrO ₂ top layer and 140 nm for the CuS layer. Copyright © 2016 John Wiley & Sons, Ltd.

The Optical Properties of ZnO Nanorods (NR) sensitized with different semiconductors in Core-Shell nanostructures were studied, comparing them with those of bare ZnO NR. Experimental measurements of Transmittance and Diffuse Reflectance show an increased light absorption at the solar spectrum and the appearances of new absorption edges (AE). The measurements are compared with numerical simulations based on Bruggeman Effective Medium Approximation. An increased absorption with the sensitizer content is observed. For similar changes in filling fractions, CdTe presents higher changes in absorption than CdS. Shifts in the AE are observed experimentally (e.g. between 2.34 eV and 2.66 eV for CdS). These shifts cannot be assigned to sensitizer content or confinement effects. A similar behaviour is observed for CdTe in which the AE measured by transmittance is between 1.31 eV and 1.36 eV, while the one obtained from Kubelka-Munk analysis of reflectance is, for the same samples, 1.57 eV and 1.49 eV, respectively. Moreover, the split-off AE is also observed at 2.55 eV and 2.28 eV. The observed large red-shifts could be associated with an enhancement of the subbandgap absorption due to an increase in the light free path at the core-shell nanostructure.