Controlled Synthesis of Nanostructured CuInS2: Study of Mechanism and Its Application in Low-Cost Solar Cells

Abstract

Various morphologies of CuInS2 (CIS) nanostructures were successfully synthesized by an oxalic acid (OA), H2C2O4, assisted solvothermal treatment. FT-IR, XRD, scanning electron microscopy, gas-sorption measurements and diffuse transmittance spectroscopy were used to characterization of CIS nanostructures. The impact of thiourea and OA concentrations, reaction temperature and reaction time on the phase structure, morphology and optical properties are investigated. The formation process is discussed and a possible growth model is proposed. OA is found to play key role during the formation process of the CIS nanostructure. Dispersion of the final nanostructures in dimethylformamide solvent forms a viscous and stable ink which can be easily deposited onto substrates. CIS nanostructures inks were applied in a cadmium-free all solution-based CuInS2 superstrate-type solar cell devices with Glass/FTO/TiO2/In2S3/CIS/Carbon structure. All processes were vacuum- and selenization-free and were done under atmospheric condition. The optimum cell shows the short-circuit current density of 13.8 mA/cm2 and the power conversion efficiency of 2.07 %, respectively. Our study outlines a general strategy for using CuInS2 nanostructures for photovoltaic application.