Physical properties of graphene oxide GO-doped ZnO thin films for optoelectronic application

This paper highlights some physical investigations on GO-doped ZnO thin films synthesized using zinc acetate dehydrate isopropyl alcohol and graphene oxide (GO) as doping element in a starting solution using a mini-spray pyrolysis process. These films, with thicknesses less than 400 nm, crystallize in hexagonal würtzite structure with a preferential orientation according to (002) direction. The morphological characterization revealed a good homogeneity at the surface with good dispersion of graphene nanoparticles over the entire surface, especially for 2% GO doping. The refractive index and thickness of ZnO:GO thin films have been calculated using the envelope method. A decrease in the refractive index with doping was observed which indicates an increase of free carriers. In addition, band gap and Urbach energies were also deducted from the absorption coefficient. Indeed, this layer provides an increase in the dielectric constant ε 2 in the IR range, which is a proof of creating free electrons. Finally, the 2% GO doping gives the best optoelectrical properties of ZnO thin films which can be used in a forthcoming application for future optoelectronics.