Influence of Sn incorporation on the properties of CuInS2 thin films grown by vacuum evaporation method

Structural, morphological and optical properties of Sn-doped CuInS2 thin films grown by double source thermal evaporation method were studied. Firstly, the films were annealed in vacuum after evaporation from 250 to 500 °C for Sn deposition time equal to 3 min. Secondly, the films deposited for several Sn evaporation times were annealed in vacuum after evaporation at 500 °C. The X-ray diffraction spectra indicated that polycrystalline Sn-doped CuInS2 films were obtained and no Sn binary or ternary phases are observed for the Sn evaporation times equal to 5 min. Scanning electron microscopy observation revealed the decrease of the surface crystallinity with increasing the Sn evaporation times and the annealing temperatures. The Sn-doped samples after annealing have bandgap energy of 1.42–1.50 eV. Furthermore, we found that the Sn-doped CuInS2 thin films exhibit N-type conductivity after annealing.