Gas pressure manipulation of exciton states in monolayer WS2

Over the past few decades, thin film optoelectronic devices based on transition metal dichalcogenides (TMDs) have made significant progress. However, the sensitivity of the exciton states to environmental change presents challenges for device applications. This work reports on the evolution of photo-induced exciton states in monolayer WS2 in a chamber with low gas pressure. It elucidates the physical mechanism of the transition between neutral and charged excitons. At 222 mTorr, the transition rate between excitons includes two components, 0.09 s-1 and 1.68 s-1, respectively. Based on this phenomenon, we have developed a pressure-tuning method for exciton manipulation, allowing a tuning range of approximately 40% in exciton weight. We also demonstrate that the intensity of neutral exciton emission from monolayer WS2 follows a power-law distribution concerning gas pressure, indicating a highly sensitive pressure dependence. This work presents a non-destructive and highly sensitive method for exciton conversion through in-situ manipulation. It highlights the potential development of monolayer WS2 in pressure sensing and explains the impact of environmental factors on product quality in photovoltaic devices.