  We demonstrate the tunability of the photoluminescence (PL) properties of
monolayer (1L)-MoS2 via chemical doping. The PL intensity of 1L-MoS2 was
drastically enhanced by the adsorption of p-type dopants with high electron
affinity, but reduced by the adsorption of n-type dopants. This PL modulation
results from switching between exciton PL and trion PL depending on carrier
density in 1L-MoS2. Achievement of the extraction and injection of carriers in
1L-MoS2 by this solution-based chemical doping method enables convenient
control of optical and electrical properties of atomically thin MoS2.
