Influence of GO and rGO on the structural and optical properties of ZnO photoelectrodes for energy harvesting applications

•ZnO:GO and ZnO:rGO composite thin films were prepared by spin coating technique.•Structural parameters are investigated by XRD spectra.•Electrical resistivity is decreased on insertion of GO and rGO, making it suitable for the photoelectrode applications. Due to excellent physical and chemical performances, graphene and its derivatives dominate the industrial and academic research aiming the commercialization, more specifically in optoelectronics-based energy harvesting. Owing to high electron movability, a lot of interest is shown in utilizing the zinc oxide (ZnO) as photoelectrode in such applications. In this study, graphene oxide (GO) and reduced graphene oxide (rGO) are synthesised through a simple modification of Hummer's method. ZnO:GO and ZnO:rGO composite thin films are deposited on glass substrates using the spin coating method. The structural, optical, and electrical properties are investigated in detail. The Fourier-transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) are used to determine the structure of the prepared films, which confirmed the presence of oxygen functionalities and the hexagonal wurtzite crystal structure. The increasing GO and rGO weight percentage has resulted in increasing the crystallite size, and in turn, decreased the resistivity. All the films exhibit transmittance around 90 % in UV–Visible region, which make them useful as an optical window in optoelectronic applications. The surface microstructure of the GO and rGO inserted samples are analysed using a high-resolution electron microscope.