1：Experimental Design and Method Selection:

The compounds were synthesized using solid-state reactions and single-crystal growth with KI flux. Crystal structures were determined using X-ray diffraction, and optical properties were measured via UV-vis diffuse reflectance spectroscopy. Theoretical calculations were performed using density functional theory (DFT).

2：Sample Selection and Data Sources:

Reagents including BaS, SrS, Cu, Ag, Fe, Ni, Sn, S, and Li2S were purchased from specified companies. Samples were prepared in molar ratios as described.

3：List of Experimental Equipment and Materials:

Silica tubes, computer-controlled furnace, Bruker D2 X-ray diffractometer, Bruker D8 Quest diffractometer, Zeiss Merlin Compact Energy Dispersive X-ray spectrometer, reflectance accessory for UV-vis spectra, Vienna ab initio simulation package (VASP) for DFT calculations.

4：Experimental Procedures and Operational Workflow:

For solid-state synthesis, reagents were sealed in silica tubes under vacuum, heated to specific temperatures (e.g., 800°C for 24 h), and cooled slowly. For single-crystal growth, powder was mixed with KI, heated, and cooled. XRD data collection, EDS testing, and optical measurements followed standard protocols.

5：Data Analysis Methods:

Structures were refined using SHELX-2016/6, band gaps were determined from reflectance spectra using direct extrapolation methods, and electronic structures were analyzed using DFT with LDA+U.