Experimental study and theoretical modeling of coating-speed-dependent optical properties of TiO2-graphene-oxide thin films

Abstract Nanostructured titanium dioxide–graphene oxide (TiO2-GO) thin films have been successfully synthesized and deposited on glass substrates using spin coating technique. TiO2-GO nanocomposites were prepared using Titanium Tetra Isopropoxide (TIP) and Graphene Oxide (GO) nanosheets. The influences of spin coating deposition speed on the structural, morphological, and optical features of the resulting TiO2-GO samples have been investigated. X-ray diffraction (XRD) patterns showed an amorphous structure of all deposited films. Scanning electron microscopy (SEM) images demonstrated that these films are homogeneous and all free from cracking over the entire surface of the sample, regardless of the number of rotations used. Atomic force microscopy (AFM) topography images reveal that all samples are smooth with very small surface roughness. Optical data obtained from UV–Vis spectrophotometer measurement together with theoretical modeling using Tauc–Lorentz (TL) oscillator model showed that all films display high transmittance level around 85% from the visible to the near-infrared region. It is also shown that an increase in spin coating speed results in a decrease in the film thickness and the optical band gap. The observed optical features reveal that TiO2-GO thin films are promising candidate that can be used as transparent conducting oxide electrode in solar cells.