Solvothermal synthesis of CuInS₂ powders and CuInS₂ thin films for solar cell application

In this study, a facile solvothermal method was developed to prepare CuInS₂ powders and CuInS₂ thin films. The CuInS₂ powders and CuInS₂ thin films were prepared by solvothermal route using the precursor of Copper (II) chloride, indium (III) nitrate, thiourea, oxalic acid, hexadecyl trimethyl ammonium bromide and ethanol. The morphology, crystallographic structure, chemical composition and optical band gap of CuInS₂ powders and CuInS₂ thin films were investigated using scanning electronic microscope (SEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS) and UV–vis spectroscopy. The results reveal that both CuInS₂ powders and CuInS₂ thin films are in chalcopyrite phase. The CuInS₂ powders are mainly composed of flower-like microspheres. Both microstructure of the sphere surface and diameter of sphere are affected by indium nitrate concentration in precursors. The CuInS₂ thin films are composed of a large number of uniform flower-like nanosheets, and the nanosheets become smaller in size and denser in distribution density with increasing concentration of thiourea. The optical band gap is found to be 1.44 and 1.52 eV for CuInS₂ powders and CuInS₂ thin films, respectively. The deposition mechanism of the CuInS₂ is discussed.