Rachid Oubaki, Karima Machkih, Hicham Larhlimi, Olayinka O. Abegunde, Jones Alami, Mohammed Makha, Mohammed, VI Polytechnic University, Benguerir, Morocco
In recent decades, there has been a significant interest in thin-film solar cells utilizing CuIn_1-xGa_xSe₂ (CIGS) as an absorbing material, reaching an efficiency of 23.6 %, attributed to the optoelectronic properties of CIGS films. However, controlling the film’s composition remains challenging, and the effect of the deposition conditions on the elemental and phase composition, particularly with the one-step sputtering, is not yet understood.
In this work, we explore the potential for controlling the elemental composition of CIGS films deposited by DcMS (Direct current Magnetron Sputtering) and HiPIMS (High Power Impulse Magnetron Sputtering) methods, by adjusting the sputtering power of a quaternary target. The structural properties were analyzed by X-ray diffraction and Raman spectroscopy, while surface morphology and chemical composition were determined by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Our results revealed that the chemical composition of the CIGS films shifts from that of the target, strongly depending on the sputtering approach and less on the sputtering power. The films consisted of a single CIGS chalcopyrite phase with no secondary phases. Furthermore, crystallinity improved with increasing sputtering power. Although HiPIMS resulted in a large deviation of chemical composition from that of the target compared to DcMS, this method produces films with smooth surfaces at relatively high deposition rates. These findings demonstrate that one-step sputtering is a viable approach to control the chemical and phase composition of CIGS. This method could simplify the manufacturing process of CIGS-based solar cells, making it more scalable for industrial production while potentially lowering costs.