Physical Properties of Sol Gel Copper Oxide (CuO) Thin Films; Sol concentration effect

Abstract

In this study, copper oxide (CuO) nanostructured thin films with different precursor concentrations (0.2, 0.4, 0.6 mol/L) were synthesized on glass substrates by the sol–gel spin coating technique. Copper chloride dihydrate, ethanol and monoethanolamine (MEA) were used as precursor, solvent and stabilizer, respectively. Structural, optical and luminescence properties of the CuO films were investigated by XRD, UV-Vis spectrometry and PL spectroscopy techniques. X-ray diffraction shows, the high crystallinity of all films with preferential orientation and crystallite size is 6 nm. Photoluminescence of all films showed emissions in the ultraviolet (UV) and several visible emissions such as violet, blue, green, yellow and red correspond to near-edge band (NBE) of CuO and the different defects in copper oxide. The average transmittance of all films is between 50 to 70 % in the visible region. A sharp absorption edge has been observed for all films in the region between 400 and 450 nm. This attributed to the absorption of light by copper oxide (CuO) thin films. The band gap was determined to be 2.7-2.9 eV (decreased with precursor concentration) that is significantly greater than the band gap of CuO bulk. Elaborated CuO films with good quality can be used in several applications such as: solar cells and photocatalysis.