Enhanced optical and electrical properties of NiO-GO composite thin films on flexible PET substrates for optoelectronic applications

Abstract

In the present work, we have reported the nickel oxide (NiO)-graphene oxide (GO) composite thin films on flexible indium tin oxide-coated poly-ethyleneterephthalate (ITO PET) substrates by a simple solution processing approach (spin coating method). The dispersion of GO nanostructures (synthesized by the modified Hummers' method) was introduced in the NiO (synthesized by the hydrothermal method) dispersion solution in different volume ratios of 1:0, 1:0.2, 1:0.5, and 1:1; and the corresponding thin films were named as NG 0, NG 2, NG 5, and NG 10, respectively. The zeta potential study reveals the moderate stability of the prepared dispersions, and the hydrodynamic diameter increases with GO inclusion in NiO dispersion. The variation of GO concentrations on the structural, morphological, optical, and electrical properties of thin films was investigated. Powder X-ray diffraction (PXRD) results reveal the crystalline structure of thin films. The morphology of the films was investigated by field emission scanning electron microscopy (FESEM), which shows the more ordered and porous hexagonal network obtained for composite films. The UV-VIS-NIR study reveals the optical properties of thin films. The optical absorption increases in the visible region with an increase in GO concentrations in composite films, and a decrease in band gap from 3.88 ​eV to 3.50 ​eV was observed for NG 2 to NG 10 thin films. The presence of Ni–O stretching and CC stretching, as well as carbon bonding with oxygen functionalities, were also confirmed by Fourier Transform Infrared (FTIR) spectroscopy. The current-voltage characteristics were measured, and the corresponding resistance of the thin films was obtained in the range of MΩ. The experimental result demonstrates the decrease in resistivity and increase in current for both forward and reverse bias ranges with the incorporation of GO in NiO thin films. The obtained results highlight the possibility of using these composite thin films for achieving good performance and suitability for flexible optoelectronic applications.