Effect of sputtering power on properties and photovoltaic performance of CIGS thin film solar cells

CuInGaS2 (CIGS) thin films were fabricated by DC magnetron sputtering by varying the sputtering power (70, 90, 110 and 130 W). The X-ray diffraction revealed the formation of tetragonal structure with (1 1 2) preferential orientation. The film prepared at 90 W has better crystallinity with minimum dislocation density and strain. From the scanning electron microscopy analysis, it was found to be a denser and larger in grain formation. The elemental quantification and stoichiometric ratio of the CIGS films were confirmed by energy-dispersive spectra. The optical band gap was found using Tauc plot, and it varied from 1.20 to 1.52 eV. The transport conduction mechanism involved in CIGS films was identified from DC four-probe method. Raman studies reveal that all the films composed of CH and CA ordering. The solar cell measurements indicate that high power conversion efficiency (η) of 0.29% and short-circuit current density of (Jsc) of 4.51 mA/cm2 obtained for the film deposited at 90 W.