Synthesis and characteristics of spray deposited CuInS2 nanocrystals thin films for photovoltaic applications

Nanocrystalline thin films of CuInS2, an attractive absorber material for highly efficient and terrestrial photovoltaic devices, were deposited on ultraclean glass substrates using spray pyrolysis technique. The prepared films were characterized by FESEM, FETEM, HRTEM, AFM, XRD, optical absorption spectroscopy, photoluminescence and current–voltage characteristics. The films exhibit almost smooth, dense and uniform topography; and have nano-sized particles 40–60 nm of CuInS2. XRD data show that the films are polycrystalline and have chalcopyrite (tetragonal) structure with crystallite size 45–60 nm. Optical absorption studies show that the band gap of spray deposited CuInS2 films is 1.55 eV, while absorption coefficient is of ∼105 cm−1. PL spectra have only one peak at 1.43 eV which may be attributed to the excitonic recombination through donor–acceptor impurity levels in the sample. Furthermore, CdS/CuInS2 heterojunction was also produced onto ITO coated glass substrate to evaluate solar cell parameters such as short circuit current density, open circuit voltage, fill factor and conversion efficiency.