Abstract: Cadmium sulfide (CdS) is an n-type semiconductor with excellent electrical conductivity that is widely used as an electron transport material (ETM) in solar cells. At present, numerous methods for preparing CdS thin films have emerged, among which magnetron sputtering (MS) is one of the most commonly used vacuum techniques. For this type of technique, the substrate temperature is one of the key deposition parameters that affects the interfacial properties between the target film and substrate, determining the specific growth habits of the films. Herein, the effect of substrate temperature on the microstructure and electrical properties of magnetron-sputtered CdS (MS-CdS) films was studied and applied for the first time in hydrothermally deposited antimony selenosulfide (Sb₂(S,Se)₃) solar cells. Adjusting the substrate temperature not only results in the design of the flat and dense film with enhanced crystallinity but also leads to the formation of an energy level arrangement with a Sb₂(S,Se)₃ layer that is more favorable for electron transfer. In addition, we developed an oxygen plasma treatment for CdS, reducing the parasitic absorption of the device and resulting in an increase in the short-circuit current density of the solar cell. This study demonstrates the feasibility of MS-CdS in the fabrication of hydrothermal Sb₂(S,Se)₃ solar cells and provides interface optimization strategies to improve device performance.