Optimization of Growth Parameters of the RF-Sputtered CuInGaSe₂ Thin Films for Photovoltaic Applications

Abstract

CuInGaSe2 (CIGS) thin films were deposited by radio-frequency sputtering using a single quaternary target and the effects of various parameters, such as substrate temperature, sputtering power, and gas flow rate, were studied. The structural, morphological, compositional, and optical properties of the films were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray, and UV-Vis-NIR spectroscopy. Samples exhibited the chalcopyrite-type tetragonal structure confirmed by XRD analysis. Raman spectroscopy showed the presence of Cu poor OVC phase in all samples.The growth of the sample at a higher substrate temperature resulted in a higher crystalline nature with a suppressed OVC phase and with an energy bandgap of 1.1eV. The deposition of CIGS at 160 W sputtering power favors growth towards (112) Bragg crystal plane, suppressing the (220)/(204) plane of CIGS, shows change in preferred orientation with a lower sputtering power at 80 and 120 W. The sample grown at 60 standard cubic centimeter per minute gas flow rate exhibited compact grain growth with marginally improved crystallinity.The sample grown at 160W, 300°C, and 60SCCM shows better crystalline and morphological properties, and it can be used as an absorber layer for highly efficient CIGS thin-film solar cells.