1：Experimental Design and Method Selection:

RF magnetron sputtering was used to deposit Cu-poor CIGS thin films on a soda-lime glass substrate with a high strain point (SS-1) using a Cu-poor CIGS target with a composition ratio of

2：

3：

4：

2 for Cu, In, Ga, and Se, respectively.

5：Sample Selection and Data Sources:

CIGS thin films were fabricated as a function of the substrate temperatures, which have different film properties.

6：List of Experimental Equipment and Materials:

RF magnetron sputtering system (ULVAC MB07-4501), 4-inch sputtering gun, Cu-poor CIGS single target (LTS chemical Co., USA), SS-1 substrate.

7：Experimental Procedures and Operational Workflow:

The sputtering chamber was evacuated to a base pressure of 2 (cid:3) 10-6 Pa. The optimized deposition conditions were as follows: RF power (300 W), ambient gas (argon), gas flow rate (30 sccm), working pressure (

8：43 Pa), and the distance between target and substrate (150 mm). Data Analysis Methods:

The crystalline structure of CIGS thin films was analyzed by X-ray diffraction (XRD, PANalytical X'pert MPD). The phase analysis was performed by Raman spectroscopy with a HeeNe laser with a wavelength of 632 nm (Jobin Yvon SAS). Plane-view and cross-section images of the CIGS thin films were examined by field-emission scanning electron microscopy (FE-SEM, Quanta 200). Optical properties were measured using a UV-VIS-IR spectrometer (Varian Cary 5000). Compositions of the CIGS thin films were measured by inductively coupled plasma (ICP, Agilent Technologies 7700x). The depth profile was analyzed by secondary ion mass spectroscopy (SIMS) system (Cameca-IMS-7f) with O2+ source ions with 150 (cid:3) 135 mm2 raster size. Finally, the photovoltaic (PV) parameters of the CIGS solar cells were measured under the simulated illumination (Solar simulator: WXS-1555S-L2, WACOM) with a light intensity of 100 mW/cm2.