Atomically thin transition-metal dichalcogenides (TMDCs) have received substantial interest due to their typical thickness-dependent optical and electronic properties and related applications in optoelectronics. However, the large-scale, thickness-tunable growth of such materials is still challenging. Herein, we report a fast growth of thickness-tunable wedding-cake-like MoS 2 flakes on 6-in. soda-lime glass by using NaCl-coated Mo foils as metal precursors. The MoS 2 thicknesses are tuned from one layer (1L) to >20L by controlling the concentrations of NaCl promoter. To attest to the ultrahigh crystal quality, related devices based on 1L-multilayer MoS 2 lateral junctions have been constructed and display a relatively high rectification ratio (â10 3 ) and extra high photoresponsitivity (â10 4 A/W). Thanks to the scalable sizes, uniform distributions of the flakes and homogeneous optical properties, the applications in ultraviolet (UV) irradiation filtering eyewear are also demonstrated. Our work should hereby propel the scalable production of layer-controlled TMDC materials as well as their optical and optoelectrical applications.