Thickness Dependent Structural and Optical Properties of Vacuum Evaporated CuIn5S8 Thin Films

The present paper reports the effect of film thickness on the structural, optical and electrical properties of vacuum evaporated CuIn5S8 thin films annealed in air atmosphere at temperature of 250 °C. The thickness of the CuIn5S8 films was varied from 100 to 900 nm. It was found that the structural properties, FWHM and grain size degraded with decreasing its thickness, however, with increasing the film thickness from 100 to 900 nm, the optical band (Eg) gap decreased from 1.76 to 1.66 eV. Hot probe method showed that all the annealed CuIn5S8 samples exhibit n-type conductivity with low resistance values in the range 100 to 400 KΩ. The band gap energy of CuIn5S8 thin films can be controlled by varying the thickness of layer and the n-type conductivity can be obtained after annealing in air atmosphere. The most significant results of the present study are that the thickness of the film can be used to modify the structural, optical and electrical properties of CuIn5S8 thin films.