Additionally, it is worth noting that the PL peak position exhibits a slower response rate to the washing procedure (Fig. ). Following a 24-hour immersion of the treated sample in Methanol solvent, the PL peak positions maintain relative stability across the monolayer flakes. This behavior is in stark contrast with the PL intensity of the treated sample, which experiences a significant decrease after the 24-hour immersion in the Methanol solvent. This differential sensitivity of the PL peak position and intensity to the rinsing procedure suggests a complex interplay of factors governing these properties. Moreover, as depicted in Fig. and S8, the subsequent Li-TFSI treatment process reveals a gradual enhancement and blueshift in the emission of 2D WS2. Interestingly, this enhancement in PL intensity, induced by the Li-TFSI treatment, exhibits a level of reversibility, suggesting the absence of any chemical reactions between FSH and Li-TFSI, as well as between Li-TFSI and the surface of 2D WS2. Based on these observations, we hypothesize that the developed treatment protocol contributes to improved p-doping and alteration of the electronic structure of 2D WS2, leading to the observed furthest blueshift and largest intensity enhancement, respectively. Besides PL, the charge-carrier mobility is a measure of semiconductor quality since it is very sensitive to impurities and traps. Here, we fabricated field-effect transistors (FETs) of WS2 monolayers and characterized the field-effect transport properties before and after treatment (Fig. ). The electrical characterizations of transistors were conducted in a high-vacuum environment (~10 -7 mbar) to eliminate extrinsic doping effects induced by air or moisture. The detailed parameters for untreated and treated devices are presented in SI Note 5 (Table and, and Fig. and). As depicted in Fig. , we observe a striking two-order increase in the field effect mobility, reaching up to 70 cm 2 V -1 s -1 at room temperature. This is the highest value achieved for mechanically exfoliated WS2 monolayer on SiO2 substrates. Such an enhancement can be attributed to the passivation of the sulfur vacancy sites, which is expected to reduce the long-range coulomb scattering. The treated FETs exhibit an average field-effect charge mobility of ~ 12 cm 2 V -1 s -1 , while that of untreated FETs is ~ 0.1 cm 2 V -1 s -1 . At the same time, we also observe small variations that can originate from different channel lengths. In addition to the 2-order enhancement in mobility upon passivation, we observe a clear decrease in the threshold voltage (VT) after the chemical treatment (Fig. ). The VT is extracted using the Extrapolated Linear Region (ELR) method, as illustrated in Fig. and. Statistically, the VT values for the treated transistors were found to be 12 ± 8 V, while the untreated transistors exhibited a larger variation, with values lying in the range of 64 ± 19 V. This shift can be attributed to the p-doping effect from the Li + ion, which is expected to decrease the concentration of trions thereby facilitating easier charge transfer across source and drain terminals. This Fermi-level shift in 2D WS2 aligns well with the PL measurements discussed above, and the DFT simulation discussed later. Notably, our SSCP protocol leads to a threeorder-of-magnitude decrease in the total FET resistance. The electrical measurements suggest a synergistic effect of increased doping and sulfur vacancy defect passivation due to the SSCP. spectral components above the noise level (detail in Supplementary Note 6, Fig. and).