A graphene-cadmium sulfide (Gr-CdS) nanocomposite was prepared by a chemical solution method, and its material properties were characterized by several analysis techniques. The synthesized pure CdS nanoparticles (NPs) and Gr-CdS nanocomposites were confirmed to have a stoichiometric atomic ratio (Cd/S = 1:1). The Cd 3d and S 2p peaks of the Gr-CdS nanocomposite appeared at lower binding energies compared to those of the pure CdS NPs according to X-ray photoelectron spectroscopy analyses. The formation of the Gr-CdS nanocomposite was also evidenced by the structural analysis using Raman spectroscopy and X-ray diffraction. Transmission electron microscopy confirmed that CdS NPs were uniformly distributed on the graphene sheets. The absorption spectra of both the Gr-CdS nanocomposite and pure CdS NPs thin films showed an absorption edge at 550 nm related to the energy band gap of CdS (~2.42 eV). The Cu(In,Ga)Se2 thin film photovoltaic device with Gr-CdS nanocomposite buffer layer showed a higher electrical conversion efficiency than that with pure CdS NPs thin film buffer layer. In addition, the water splitting efficiency of the Gr-CdS nanocomposite was almost three times higher than that of pure CdS NPs.
Keywords: Cu(In; Ga)Se2; Gr–CdS; buffer layer; cadmium sulfide; water splitting.