Sol-gel synthesized spin coated GO:ZnO composite thin films: optical, structural and electrical studies

In the present work, we report on the structural, optical and electrical properties of solution-processed transparent conducting Graphene Oxide and Zinc oxide (GO: ZnO) composite thin films. Ecofriendly top-down modified Hummer's method was adopted for the synthesis of GO. The ZnO and GO:ZnO thin films were grown on the glass substrates employing a simple and cost-effective spin coating technique. To get a stable solution for spin coating, an efficient solvent, 2-methoxyethanol is used to disperse GO. The structural properties of the GO: ZnO thin films were analyzed using XRD pattern wherein the average crystallite size decreases with the increase in GO% in ZnO. UV-vis spectroscopy studies showed that the optical band gap and the transmittance (>80%) of thin films are decreased with the increment of GO% in ZnO. FESEM and XRD data revealed a decrease in the particle size. GO: ZnO composite thin films exhibit an ohmic nature when silver is used as a contact with increase in current in composite thin films compared to ZnO thin film. The increase in current is due to the removal of oxygen moieties in GO and partial restoration of the graphene structure occurred during the pre and post-annealing of thin films. Thus, the reduced graphene oxide (rGO) acts as a conductive frame for ZnO. The optical and electrical parameters procured for GO: ZnO composite thin films propel the possibility of using composite thin films for transparent conducting electrode applications.