Investigation of CuInS2 thin films deposited on FTO by one-pot solvothermal synthesis

CuInS2 thin films were deposited with fix different thiourea (TU) concentrations on fluorine-doped tin oxide-coated (FTO) conductive glass substrates by a facile and rapid solvothermal method. XRD analysis shows that all CuInS2 thin films crystallize in a chalcopyrite structure with a preferential orientation along (112) direction, and the average crystallize sizes of the nanoparticles are 20–50 nm. The X-ray photoelectron spectroscopy (XPS) shows that the S deficiency decreases with increasing TU concentration. Surface morphology studies show the CuInS2 thin films are composed of nanoplates or sphere-like. The thicknesses of the CuInS2 thin films can be adjusted from 0.33 to 2.1 μm by controlling the TU concentration. The average absorption of all CuInS2 thin films is greater than 90% in the wavelength ranging from 400 to 950 nm, and the band gaps of all CuInS2 thin films are in the range of 1.52–1.90 eV. As shown in room temperature photoluminescence (PL), the as-synthesized CuInS2 thin films have a near-infrared emission at 1.54 eV and an orange–red emission at 1.92 eV in visible spectrum.