This study demonstrates the tunable photoluminescence (PL) properties of monolayer MoS₂ via chemical doping. The PL intensity of 1L-MoS₂ was significantly enhanced by p-type dopants, while it was reduced by n-type dopants. This modulation is attributed to the switching between exciton and trion PL depending on the carrier density in 1L-MoS₂. The solution-based chemical doping method enables convenient control of the optical and electrical properties of atomically thin MoS₂. Monolayer transition-metal dichalcogenides (TMDs) have attracted significant attention due to their potential applications in optoelectronic devices. MoS₂ and its analogues are promising candidates for two-dimensional direct-band-gap semiconductors. The optical properties of 1L-MoS₂ are influenced by the carrier density, and the interplay between excitons and charge carriers leads to the formation of trions, which provide additional pathways for controlling the optical properties. The study shows that the PL intensity of 1L-MoS₂ can be tuned using solution-based chemical doping. P-type dopants, such as F₄TCNQ and TCNQ, enhance the PL intensity by switching the dominant PL process from trion recombination to exciton recombination. In contrast, n-type dopants, such as NADH, reduce the PL intensity by suppressing exciton PL through electron injection. These results indicate that chemical doping can bidirectionally control the Fermi level of 1L-MoS₂, offering a significant advantage in controlling its optical and electrical properties. The study also investigates the effect of different p-type and n-type dopants on the PL properties of 1L-MoS₂. The PL intensity is enhanced by p-type dopants and suppressed by n-type dopants, demonstrating the opposite behavior for different dopants. The chemical doping mechanism is supported by the flat band potential of few-layer MoS₂ and the electron transfer between dopants and MoS₂. The PL intensity of excitons and trions was analyzed using a three-level model, which includes excitons, trions, and the ground state. The results show that the PL intensity of excitons increases with the number of doping steps, while the PL intensity of trions decreases. The total PL intensity of peak A increases due to the enhancement of exciton PL. The study provides strong evidence for the chemical doping mechanism in 1L-MoS₂. The PL intensity of 1L-MoS₂ is dominated by exciton PL after p-type doping, indicating that excitons can recombine without forming trions due to the reduction in excess carriers. The results suggest that both electron extraction and injection in 1L-MoS₂ can be achieved via solution-based chemical doping, offering a convenient method for tuning the optical and electrical properties of atomically thin TMDs.This study demonstrates the tunable photoluminescence (PL) properties of monolayer MoS₂ via chemical doping. The PL intensity of 1L-MoS₂ was significantly enhanced by p-type dopants, while it was reduced by n-type dopants. This modulation is attributed to the switching between exciton and trion PL depending on the carrier density in 1L-MoS₂. The solution-based chemical doping method enables convenient control of the optical and electrical properties of atomically thin MoS₂. Monolayer transition-metal dichalcogenides (TMDs) have attracted significant attention due to their potential applications in optoelectronic devices. MoS₂ and its analogues are promising candidates for two-dimensional direct-band-gap semiconductors. The optical properties of 1L-MoS₂ are influenced by the carrier density, and the interplay between excitons and charge carriers leads to the formation of trions, which provide additional pathways for controlling the optical properties. The study shows that the PL intensity of 1L-MoS₂ can be tuned using solution-based chemical doping. P-type dopants, such as F₄TCNQ and TCNQ, enhance the PL intensity by switching the dominant PL process from trion recombination to exciton recombination. In contrast, n-type dopants, such as NADH, reduce the PL intensity by suppressing exciton PL through electron injection. These results indicate that chemical doping can bidirectionally control the Fermi level of 1L-MoS₂, offering a significant advantage in controlling its optical and electrical properties. The study also investigates the effect of different p-type and n-type dopants on the PL properties of 1L-MoS₂. The PL intensity is enhanced by p-type dopants and suppressed by n-type dopants, demonstrating the opposite behavior for different dopants. The chemical doping mechanism is supported by the flat band potential of few-layer MoS₂ and the electron transfer between dopants and MoS₂. The PL intensity of excitons and trions was analyzed using a three-level model, which includes excitons, trions, and the ground state. The results show that the PL intensity of excitons increases with the number of doping steps, while the PL intensity of trions decreases. The total PL intensity of peak A increases due to the enhancement of exciton PL. The study provides strong evidence for the chemical doping mechanism in 1L-MoS₂. The PL intensity of 1L-MoS₂ is dominated by exciton PL after p-type doping, indicating that excitons can recombine without forming trions due to the reduction in excess carriers. The results suggest that both electron extraction and injection in 1L-MoS₂ can be achieved via solution-based chemical doping, offering a convenient method for tuning the optical and electrical properties of atomically thin TMDs.