“…Two-dimensional transition metal dichalcogenides (2D-TMDs) are beyond-graphene layered materials that have become the new platform for studying the physics of 2D semiconductors. With atomically thin layers confined in a 2D plane, 2D-TMDs manifest remarkable properties including indirect-to-direct band gap switching, emergent photoluminescence, strong photovoltaic response, anomalous lattice vibrations, strong light–matter interactions at heterojunctions, valley-selective circular dichroism, excitonic dark states, control of valley polarization using optical helicity, and field-induced transport with a current ON–OFF ratio exceeding 10 8 , that give 2D-TMDs immense potential for transistors, photodetectors, sensors, and many other applications. − Among the variety of materials being investigated, the thinnest semiconductor, molybdenum disulfide (2D-MoS 2 ), exhibits promising prospects for low-cost, highly sensitive, and flexible next-generation optoelectronic, nanoelectronic, photovoltaic, and valleytronic applications. Unlike graphene that does not manifest a band gap, 2D-MoS 2 has a layer thickness-dependent band gap, which is indirect in the bilayer and above but becomes direct in the monolayer limit .…”