Synthesis, Structural and Optical Characterization of Spray-Deposited CuInS₂ Thin Films

Polycrystalline nano-structured CuInS2 thin films have been prepared by chemical spray-pyrolysis of aqueous solution of Copper Chloride, Indium Chloride and Thiourea onto heated glass substrate. The structural, morphological, optical absorptions properties of the CuInS2 thin films have been systematically studied to understand the effect of various preparative parameters like substrate temperature, Tc, Hydrogen ion concentration (pH) and ion ratio (Cu/In) of the spray solution. It is observed that the parameters critical to structural and optical properties of sprayed CuInS2 films are substrate temperature and ion ratio of Cu/In in the spraying solution. The X-ray diffraction patterns confirm that the use of copper rich solutions reduce the temperature required for single phase composition of CuInS2 films from 375 0C (Cu/In = 1.0) to 300 0C (Cu/In = 1.2). The absorption coefficient α was calculated from transmittance and reflectance measurements over a large spectral range (300–2500 nm). The optical data have been analyzed to evaluate the optical band gap. The average film thickness and refractive index were calculated from ellipsometeric data.