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

Abstract

CuInGaSe2 (CIGS) thin films were deposited by RF sputtering using a single quaternary target. The effects of various sputtering parameters, such as substrate temperature, sputtering power, and gas flow rate, were studied systematically. The structural, morphological, compositional, and optical properties of the films were investigated by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), and UV–vis-NIR spectroscopy. The samples exhibited the chalcopyrite type tetragonal structure of CIGS, as confirmed by the XRD analysis. Raman spectroscopy represents the presence of Cu poor ordered vacancy compound (OVC) phase in all the present samples. The growth of the sample at a higher substrate temperature resulted in a higher crystalline nature with a suppressed OVC phase and energy bandgap of 1.18 eV. 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 a gas flow rate of 60 standard cubic centimeters per minute (SCCM) exhibited compact grain growth with marginally improved crystallinity. The sample grown at 160 W, 300 °C, and 60 SCCM showed better crystalline and morphological properties, and it can be used as an absorber layer for highly efficient CIGS thin-film solar cells.