Manipulation of exciton and trion quasiparticles in monolayer WS2 via charge transfer

Charge doping in transition metal dichalcogenide is currently a subject of high importance for future electronic and optoelectronic applications. Here we demonstrate chemical doping in CVD grown monolayer (1L) of WS2 by a few commonly used laboratory solvents by investigating the room temperature photoluminescence (PL). The appearance of distinct trionic emission in the PL spectra and quenched PL intensities suggest n-type doping in WS2. The temperature-dependent PL spectra of the doped 1L-WS2 reveal significant enhancement of trion emission intensity over the excitonic emission at low temperature indicating the stability of trion at low temperature. The temperature dependent exciton-trion population dynamic has been modeled using the law of mass action of trion formation. These results shed light on the solution-based chemical doping in 1L WS2 and its profound effect on the photoluminescence which is essential for the control of optical and electrical properties for optoelectronics applications.