Influence of ytterbium (Yb) dopant on the optical properties of electrochemically deposited zinc oxide (ZnO) films

Abstract

Undoped and ytterbium-doped ZnO films were synthesized on fluorine-doped tin oxide (FTO) conductive substrates using zinc nitrate hexahydrate (Zn(NO3).6H2O), sodium hydroxide (NaOH), ytterbium nitrate penta-hydride (Yb (NO3)3.5H2O) as sources of Zn2+, O2− and Yb2+ ions respectively through electrodeposition method. The structure, elemental composition, and optical features were determined via x-ray diffractometry (XRD), Energy dispersive x-ray spectroscopy (EDX), UV–visible spectrophotometry (UV–vis), four-point probe technique, and scanning electron microscopy respectively. The impact of Yb on ZnO crystallographic, elemental, optical, and energy band gap features of the ZnO materials have been studied. Structural results revealed polycrystalline films while the EDX spectrum affirms the presence of the basic elemental composition of deposits. The optical result showed high absorbance feature and decreased energy band gaps of zinc oxide films after introducing ytterbium as dopant. The energy band gap value observed for the undoped zinc oxide film which was 3.05 eV recorded a decreased range from 2.79 eV to 2.64 eV upon doping. The films exhibited increasing resistivity with thickness and granular nanocrystals distributed over the substrate surface. The low transmitting property and decreased energy band gaps of the Yb-doped ZnO films make it useful materials for solar thermal energy collectors and photovoltaic applications.