Abstract
The illumination of monolayer transition metal dichalcogenides can dynamically photoionize donor centers, increasing the concentration of free carriers. Here, we investigate the effect of such photodoping on the interlayer exciton formed across a MoS2/MoSe2/MoS2 heterostructure. We first identify the photodoping effect by monitoring the increase in the trion dissociation energy, accompanied by a characteristic tuning of the exciton/trion photoluminescence (PL) intensity ratio in MoSe2 upon exposure to laser light. At the same time, the PL intensity of the interlayer exciton significantly decreases, while the combined PL intensity of the exciton and the trion in MoSe2 is enhanced, showing that the interlayer charge transfer can be controlled by the doping level. This effect is persistent on a timescale of several hours, provided that the sample is maintained under vacuum, suggesting a mechanism involving laser induced desorption of molecules physisorbed on the surface of the heterostructure. This hypothesis is supported by the observation of a significantly faster photodoping effect when the sample is excited with a pulsed laser with the same average power.
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