Solid-state synthesis and effect of temperature on optical properties of Cu-ZnO, Cu-CdO and CuO nanoparticles

Controlling novel morphologies and developing effective doping strategies are two important tasks for advancing ZnO and CdO based nanomaterials. Modulation of band energies through size control offers new ways to control photoresponse and photoconversion efficiencies of the solar cell. The P-type semiconductors of copper oxide and zinc oxide are an important functional material used for photovoltaic cells. CuO is attractive as a selective solar absorber since it has high solar absorbance and a low thermal emittance. This work describes the synthesis and characterization of semiconducting nanoparticles (ZnO, CuO, CdO, Cu-ZnO, Cu-CdO) via one-step, solid-state reaction in the presence of polyethylene glycol 400. Solid-state mechanochemical processing which is not only a physical size reduction process in conventional grinding but also a chemical reaction that is mechanically activated at the nanoscale during grinding. The present method is a simple and efficient method for the preparation of nanoparticles with high yield at low cost. The structural and chemical composition of the nanoparticles were analyzed by X-ray diffraction, field emission scanning electron microscopy and energy-dispersive spectrometer (FESEM/EDAX). Optical properties and band gap were studied by UV-vis absorption spectra. XRD data has been concluded that the Cu doping induced the lattice constants to change to some extent. These results have showed that the band gap energy decreases with increase in annealing temperature, which can be attributed to the improvement in crystallinity of the samples. The band gap of the Cu-ZnO and Cu-CdO crystals can be tuned in the range of 3.34-3.28 eV and 2.80-2.21 eV respectively, by the use of dopants. (C) 2011 Elsevier B.V. All rights reserved.