Effect of Zinc Incorporation in CuInS2 Thin Films Grown by Vacuum Evaporation Method

Structural, optical and electrical properties of Zn-doped CuInS2 thin films grown by double source thermal evaporation method were studied. Evaporated thin films were grown from CuInS2 powder by vacuum evaporation using resistively heated tungsten boats. The element Zn was evaporated from a thermal evaporation source. The amount of the Zn source was determined to be 0-4% molecular weight compared with CuInS2 source. The effects of Zn on films properties were investigated using X-ray diffraction, optical transmission and reflection spectra. The films were annealed in vacuum at 260 degrees C for 2 h. The Zn-doped samples have band-gap energy of 1.474-1.589 eV. We found that the Zn-doped CuInS2 thin films exhibit p-type conductivity and we predict that Zn species can be considered as suitable candidates for use as doped acceptors to fabricate CuInS2-based solar cells.