Large area thin films of Cu(In,Ga)Se-2 (CIGS) were grown by sequential sputtering. Photovoltaic cells have been fabricated using these films and the performance has been characterized. The effect of annealing conditions (temperature and duration) of the CIGS film on the device performance has been investigated. SEM studies of the films correlate the microstructure of the CIGS films with the solar cell efficiency. Cell efficiencies in excess of 10% have been achieved by using optimized annealing conditions. The optical properties of the CIGS films were characterized using Variable Angle Spectroscopic Ellipsometry (VASE). The Gaussian broadened polynomial superposition (GBPS) parametric relationship is used to describe the optical properties of CIGS films below, above and through the bandgap energy. The present results show that spectroscopic ellipsometry may be used in situ to monitor and optimize him growth conditions and achieve high efficiencies.