Characterization of sol gel synthesized undoped . and copper (II)-doped zinc oxide thin films

Abstract

Thin films of undoped and copper (II) -doped ZnO have been synthesized on amorphous and conducting glass substrates using spin coating technique. The molar ratio of <chemical formular> to <chemical formular> in the initial mixture was varied up to 5%. Speed of spin coating system and initial precursor solution were varied to optimize the properties of samples. The morphological and optical properties of the thin films as a function of <chemical formular> content have been investigated using atomic force microscopy and UV-Visible spectrophotometry, respectively. Film thickness varies in a random manner depending on the amount of ZnO or copper (II) - doped ZnO spread on the substrate. The calculated energy gap values of doped ZnO film samples decrease with the molar percentage of <chemical formular> in ZnO. The photocell was prepared using doped or undoped ZnO film, platinum electrode and KI/h liquid electrolyte . (I-V) characteristics of the cells were measured under the dark condition and illumination of 1000 mW (cm-2) (AM 1.5) simulated sunlight. I-V curves of the thin films indicate that photo current increases with the doping molar percentage of < chemical formular > by implying that the efficiency in electron-hole formation increases with the decrease of band gap. However, a significant efficiency of 0.13 ~ could be obtained only in 5% of < chemical formular > doping while other doping molar percentages result an average efficiency of 0.07%. All results indicated significant influence on optical and electrical properties of ZnO under trace amounts of copper doping.