Solution-processed CuO thin films with various Cu2+ ion concentrations

Presented herein is a report on cupric oxide (CuO) thin films prepared on glass substrates by using a solution process with varying nominal concentrations of Cu2+ ions at 0.15 M, 0.20 M, and 0.25 M. X-ray diffraction patterns and scanning electron microscopy (SEM) micrographs were analyzed to evaluate the crystalline structure and surface morphology of the CuO thin films. The fabricated CuO thin films exhibited a single-phased monoclinic structure with (200) and (111) orientations. The grain size of the CuO thin films was observed to increase with higher concentration, by SEM observation. The electrical and optical properties of the CuO thin films were investigated using a four-probe measurement system and UV/VIS spectrometer, respectively. The thin films showed a minimum resistivity of 0.085 Ω cm corresponding to the 0.25 M concentration, and a bandgap energy ranging from 2.10 eV to 2.15 eV. In addition, the light-harvesting ability of CuO thin films was considered by the absorption figure of merit (a-FOM), in correlation with the global solar spectrum. A maximum a-FOM value of 12.79 Ω−1 cm−1 was attained for the sample with a Cu2+ ion concentration of 0.25 M.