Effect of [Cu]/[In] ratio on properties of CuInS2 thin films prepared by successive ionic layer absorption and reaction method

CuInS2 ternary films were prepared by a soft solution processing, i.e. successive ionic layer absorption and reaction (SILAR) method. The films were deposited on glass substrates at room temperature and heat-treated under Ar atmosphere at 500 °C for 1 h. CuCl2 and InCl3 mixed solutions with different ionic ratios ([Cu]/[In]) were used as cation precursor and Na2S as the anion precursor. The effect of the [Cu]/[In] ratio in precursor solution on the structural, chemical stoichiometry, topographical, optical and electrical properties of CuInS2 thin films was investigated. XPS results demonstrated that stoichiometric CuInS2 film can be obtained by adjusting [Cu]/[In] ratios in solution. Chalcopyrite structure of the film was confirmed by XRD analysis. The near stoichiometric CuInS2 film has the optical band gap Eg of 1.45 and resistivity decreased with increase of [Cu]/[In] ratios.