Terbium(III) sulfide is primarily used in optoelectronic and luminescent applications due to its favorable photoluminescence properties. It serves as a dopant in phosphors for fluorescent lamps and display technologies, where it emits green light under ultraviolet excitation, contributing to high color rendering and efficiency. The compound is also investigated for use in solid-state lighting, such as LEDs, and in infrared optical materials because of its stability and electronic structure. Additionally, it finds application in semiconductor research, particularly in the development of rare-earth chalcogenides for advanced electronic and thermoelectric devices.