Transition metal dichalcogenides (TMDs) have attracted tremendous attention and played an important role in the development of two-dimensional (2D) semiconductor materials in the past decade due to their unique physical properties and outstanding photoelectric performance[1–3]. The extraordinary physical properties of the TMDs can be attributed to their unique physical structure. TMDs are layered structures, in which monolayer materials are stacked together through weak van der Waals forces between layers. As a result, the optical and physical properties of TMDs will always exhibit striking layer-dependent evolutions[5,6]. Peculiarly, when the material is thinned from multiple layers to an atomically thin monolayer, the indirect band gap semiconductor will be transformed into a direct band gap semiconductor. Due to its fascinating and layer-dependent photoelectronic and mechanical properties, 2D TMDs have promising potential applications in the field of optoelectronics, electronics, and flexible devices[8–11].