Electrodeposition and characterization of ZnO thin films using sodium thiosulfate as an additive for photovoltaic solar cells

Abstract

Zinc oxide thin films have been grown by electrodeposition technique onto Cu and ITO-coated glass substrates from an aqueous zinc nitrate solution with addition of sodium thiosulfate at 90℃.The effects of sodium thiosulfate on the electrochemical deposition of ZnO were investigated by cyclic voltammetry and chronoamperometry techniques.Deposited films were obtained at-0:60 V vs.SCE and characterized by XRD, SEM, FTIR, optical, photoelectrochemical and electrical measurements.Thickness of the deposited film was measured to be 357 nm.X-ray diffraction results indicated that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along (002) plane.FTIR results confirmed the presence of ZnO films at peak 558 cm -1 .SEM images showed uniform, compact morphology without any cracks and films composed of large flower-like ZnO agglomerates with star-shape.Optical properties of ZnO reveal a high optical transmission (>80%) and high absorption coefficient ( α >105 cm -1 ) in visible region.The optical energy band gap was found to be 3.28 eV.Photoelectrochemical measurements indicated that the ZnO films had n-type semiconductor conduction.Electrical properties of ZnO films showed a low electrical resistivity of 6.54 Ω·cm, carrier concentration of-1.3×10 17 cm -3 and mobility of 7.35 cm 2 V -1 s -1 .