Antimony sulfide (Sb₂S₃) is a promising absorber for low-cost optoelectronic applications but suffers from limited near-infrared absorption and charge transport. In this study, a simple chemical bath deposition approach was employed to enhance Sb₂S₃ thin films through copper (Cu) doping. The introduction of Cu plays a decisive role by improving crystallinity, narrowing the bandgap from 1.72 to 1.69 eV, and enhancing visible-light absorption. Structural and optical analyses confirmed successful Cu incorporation without secondary phases and with reduced defect states. Photovoltaic tests further demonstrated an increase in short-circuit current density (16→18 mA cm⁻²) and a 12.5% efficiency improvement. These results highlight that Cu doping is not only a practical route to overcome the intrinsic limitations of Sb₂S₃ but also a scalable strategy to optimize its performance for efficient optoelectronic and photovoltaic applications.