Surfactant-mediated growth of nanostructured zinc oxide thin films via electrodepositionand their photoelectrochemical performance

Abstract

Zinc oxide (ZnO) thin films were electrodeposited from an aqueous zinc acetate solutiononto fluorine-doped thin oxide (FTO) coated conducting glass substrates. The effect oforganic surfactants like polyvinyl pyrrolidone (PVP), sodium dodecyl sulfate (SDS),polyethylene glycol (PEG), ethylene glycol (EG) and polyvinyl alcohol (PVA) on theirstructural, morphological, optical and photoelectrochemical properties was studied. Thex-ray diffraction patterns revealed the formation of phase-pure ZnO thin films. The filmsdeposited using organic surfactants exhibit different surface morphologies. It was observedthat the organic surfactants play important roles in modifying the surface morphology andsize of the crystallites. A compact granular morphology was observed for the ZnOsamples grown without organic surfactants. The films exhibit nanoparticles of size100–150 nm for PVP, EG and PVA mediated growth. The vertically aligned thin andcompact hexagonal crystallites stem from the SDS, whereas microporous corrugatedmorphology is observed for PEG-mediated growth. All the samples exhibit roomtemperature photoluminescence (PL). Oxygen vacancies contribute to the activeluminescent centers for the emission of green light in ZnO thin films. PL getsquenched for the SDS surfactant. All the samples were post-treated with ethanol toremove stray surfactant molecules. FTIR study was used to confirm the removalof adsorbed surfactant molecules from the samples. Moreover the samples arephotoelectrochemically (PEC) active and exhibit the highest photocurrent of231 µA, a photovoltage of 492 mV and 0.42 fill factor for the ZnO:SDS films.