Hydrothermal growth of reduced graphene oxide doped with nitrogen and sulfur for photodiode applications

Abstract In this study, reduced graphene oxide (rGO) is synthesized using various reducing agents through a hydrothermal method and subsequently employed in fabricating photodiodes. Initially, graphene oxide (GO) is synthesized, and its molecular structure, crystalline nature, and morphology are examined using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Hydrazine hydrate, thiourea, and their mixture are used as reducing agents to produce rGO. The results showed that rGO synthesized using hydrazine hydrate and the mixture of hydrazine hydrate and thiourea exhibited a crystalline structure, whereas rGO synthesized using thiourea alone had an amorphous structure. The optical properties, including the absorption and photoluminescence spectra of the prepared rGO, are investigated. X-ray photoelectron spectroscopy (XPS) is used to analyze the reduction of GO and the doping of nitrogen (N) and sulfur (S) atoms. The three types of rGO are dispersed in chlorobenzene, and the solutions are sonicated to ensure homogeneity. These solutions are then deposited onto n-Si substrates to fabricate photodiodes. The current–voltage (I-V) characteristics of the diodes are measured under dark and illuminated conditions. Key diode parameters, including the ideality factor, potential barrier height, and series resistance, are calculated for all three devices. The photoconduction behavior of the diodes is also analyzed, and their photosensitivity and photoresponsivity are estimated and compared to evaluate the performance of the heterojunction diodes.