2D semiconductor tungsten disulfide (WS2), a member of transition metal dichalcogenides (TMDCs), attracts significant interest in both fundamental physics and many promising applications, such as light emitters, photodetectors/sensors, and flexible nanoelectronics, due to its fascinating optical, electronic, and mechanical properties. Its layer-dependent bandgap—transitioning from a direct bandgap of ~2.1 eV in the monolayer to an indirect bandgap of ~1.3 eV in the bulk—combined with its high aspect ratio, high carrier mobility, and robust chemical and thermal stability, makes WS₂ a compelling candidate for next-generation optoelectronic technologies. Structurally, WS₂ comprises a trilayer fundamental unit in which a plane of W atoms is sandwiched between two planes of S atoms, with adjacent layers held together by weak van der Waals (vdW) forces. This bonding facilitates easy mechanical cleavage and produces ultraclean surfaces free of dangling bonds, enabling the fabrication of high-quality vdW heterostructures. Such heterojunctions have been widely utilised in advanced photodetectors, sensors, and light-emitting devices.