Experimental and theoretical studies of CuInS₂ thin films for photovoltaic applications

CuInS₂ thin films were synthesized by spray pyrolysis. The films were characterized using X-ray diffraction, Raman spectroscopy, and spectrophotometer (UV–Vis). The structural studies reveal that CuInS₂ thin films are of chalcopyrite phase. The complex dielectric constants (ε_r and ε_i), the refractive index (n), extinction coefficient (k), absorption coefficient (α), gap energy (E_g), and the optical conductivity (σ) were calculated. The obtained results are suitable for photovoltaic applications. To confirm our experimental results, a series of Ab initio calculations was performed. The generalized gradient approximation and the mBJ potential for the exchange–correlation potential have been used to calculate the band structure, density of states, charge density, and optical properties of CuInS₂.