Emission enhancement and exciton species modulation in monolayer WS2 via decoration of CdTe quantum dots

Transition metal dichalcogenides MX2 (M = Mo/W; X = S/Se) exhibit excellent optical and electrical properties. However, the atomically thin thickness induced low absorption cross sections impede their further applications as efficient absorbers and emitters. Herein, we report the emission enhancement and exciton species modulation in monolayer (ML) WS2 via the decoration of CdTe quantum dots (QDs). The ML WS2 was synthesized by thermal evaporation and showed evident neutral (A(o)) and charged (A(-)) exciton emissions with variable A(-)-to-A(o) ratios under different excitation powers and temperatures. The A(-) emission played an important role at low temperature (80 K) and high excitation power (5 mW). After the decoration of the CdTe QDs, the photoluminescence (PL) intensity of the ML WS2 enhanced greatly. Moreover, the A(o) emission was dominant in WS2 + CdTe even under high excitation power and low temperature. The transfer of numerous holes from CdTe to WS2 induced the nonradiative recombination probability reduction, and p-type doping was critical to the observed PL enhancement and exciton species modulation in WS2 + CdTe. Our results provide a flexible strategy to improve the PL properties of atomically thin WS2 and further deepen the understanding of exciton-physics in ML MX2 for various applications. Published under an exclusive license by AIP Publishing.