The study demonstrates the tunable photoluminescence (PL) properties of monolayer (1L)-MoS₂ through chemical doping. The PL intensity of 1L-MoS₂ is significantly enhanced by adsorbing p-type dopants with high electron affinity, while it is reduced by adsorbing n-type dopants. This modulation results from switching between exciton PL and trion PL based on carrier density in 1L-MoS₂. The solution-based chemical doping method enables convenient control of the optical and electrical properties of atomically thin MoS₂. The findings suggest that both carrier extraction and injection in 1L-MoS₂ can be achieved through chemical doping, providing a strong advantage in tuning the properties of atomically thin transition-metal dichalcogenides (TMDs).The study demonstrates the tunable photoluminescence (PL) properties of monolayer (1L)-MoS₂ through chemical doping. The PL intensity of 1L-MoS₂ is significantly enhanced by adsorbing p-type dopants with high electron affinity, while it is reduced by adsorbing n-type dopants. This modulation results from switching between exciton PL and trion PL based on carrier density in 1L-MoS₂. The solution-based chemical doping method enables convenient control of the optical and electrical properties of atomically thin MoS₂. The findings suggest that both carrier extraction and injection in 1L-MoS₂ can be achieved through chemical doping, providing a strong advantage in tuning the properties of atomically thin transition-metal dichalcogenides (TMDs).