Ultrathin layered MoS2 and N-doped graphene quantum dots (N-GQDs) anchored reduced graphene oxide (rGO) nanocomposite-based counter electrode for dye-sensitized solar cells

Abstract

Numerous inorganic and organic counter electrodes (CEs) have been fabricated for dye-sensitized solar cells (DSSCs) instead of platinum (Pt) CE. However, MoS2 and carbon nanocomposite have played an important role in CEs due to their superior electrochemical properties and high chemical stability. N-doped graphene quantum dot (N-GQD) @ MoS2 @ reduced graphene oxide (rGO) nanocomposite was synthesized by the two-step hydrothermal method. The morphology of as-synthesized nanocomposites was studied using field emission scanning electron microscope (FE-SEM) and scanning transmission electron microscopy (STEM). It confirms the formation of sphere-like MoS2 composed of nanosheets on the surface of rGO sheets. The N-GQD@MoS2@rGO composites confirmed the presence of MoS2, rGO, and N-GQD by X-ray diffraction (XRD) and Raman spectra. The chemical composition and purity of N-GQD@MoS2@rGO was examined by the X-ray photoelectron spectroscopy analysis technique. The electrochemical property of the as-fabricated CEs was studied by cyclic voltammetry (CV) analysis by using the iodine-based electrolyte. The N-GQD@MoS2@rGO shows the superior catalytic property due to more electrochemical active site and electrical conductivity property of rGO and MoS2. The DSSCs device assembled with as-fabricated CEs and their photovoltaic power conversion efficiency (η) of MoS2 was 2.01%, MoS2@rGO was 3.92%, N-GQD@MoS2 was 3.53%, N-GQD@MoS2@rGO was 4.65%, and Pt was 5.17%.