Effect of annealing treatment and deposition temperature on CdS thin films for CIGS solar cells applications

Present study expounds how post-deposition annealing affects the various structural and optical properties of CdS thin films deposited by chemical bath deposition technique. The structural and morphological changes have been observed by X-ray diffraction (XRD), field emission scanning electron microscopy, Transmission electron microscopy and atomic force microscopy studies; however, the optical and electrical properties of the as deposited and annealed films were studied by UV-Vis spectroscopy and four probe method, respectively. The energy dispersive X-ray analysis confirmed that all as-deposited and annealed films showed almost stoichiometric composition. XRD pattern of the thin films clearly shows the transformation from the cubic structure to the hexagonal structure induced by annealing. The band gaps of the as deposited films were found in the range of 2.41-2.47 eV, while after annealing it decreases due to the decomposition of hydroxides. The electrical resistivity found to decrease approximately 10 times after annealing the as-deposited CdS thin films.