Coupled Charge Transfer Dynamics and Photoluminescence Quenching in Monolayer MoS(2) Decorated with WS(2) Quantum Dots

Herein, we have investigated the tunability of the photoluminescence (PL) of the monolayer MoS(2) (1L-MoS(2)) by decorating it with WS(2) quantum dots (WS(2) QD). The direct bandgap 1L-MoS(2) and WS(2) QDs are grown by chemical vapor deposition and liquid exfoliation methods, respectively. The room temperature PL spectrum of bare 1L-MoS(2) is systematically quenched with its decoration with WS(2) QDs at different concentrations. A decrease in the work function of 1L-MoS(2) with the decoration of WS(2) QDs was established from the Kelvin probe force microscopy analysis. A detailed quantitative analysis using the four-energy level model involving coupled charge transfer was employed to explain the redshift and the systematic decrease in the intensity of the PL peak in 1L-MoS(2)/WS(2) QD heterostructure. The modulation of the PL in the heterostructure is attributed to the increase in the formation of negative trions through the charge transfer from WS(2) QD to the 1L-MoS(2) and thus making the 1L-MoS(2) heavily n-type doped, with increase in the electron density by ~1.5 × 10(13) cm(−2). This study establishes the contribution of defects in the coupled charge transfer dynamics in 1L-MoS(2), and it lays out a convenient strategy to manipulate the optical and electrical properties of 1L-MoS(2) for various optoelectronic applications.