Robust and High Photoluminescence in WS2 Monolayer through In Situ Defect Engineering

The photoluminescence quantum yield (PLQY) of the chemical vapor deposition (CVD) grown transition-metal dichalcogenides (TMDs) films is often much lower than their mechanically exfoliated counterparts, making the coexistence of large-area and high PLQY in TMDs monolayer a huge challenge. Here, an in situ defect engineering strategy is reported to fundamentally dilutes the impact of intrinsic sulfur vacancy on tungsten disulfide (WS2) monolayer. By ingeniously incorporating oxygen atoms in the sulfur vacancy sites of WS2 lattice via the CVD method, oxygen doped WS2 monolayer exhibits remarkably improved optical properties. The PLQY is uniformly enhanced by nearly two orders and can reach up to 9.3%, which is even higher than mechanically exfoliated counterparts. Besides, strong W-O bonds endow materials with superior environment stability, and the high PLQY could persist with an endurance of up to 3 months under ambient conditions without any protection. More in-depth insights from the first-principle calculations illustrate that the enhancement mechanism is the synthetic action of the suppression of nonradiative recombination and conversion from trion to neutral, and the excellent stability arises from repaired saturated coordination bonds at sulfur vacancy sites. This method opens up more possibilities for both fundamental exciton physics and optoelectronics applications.