Spatiotemporally Controlled Access to Photoluminescence Dark State of 2D Monolayer Semiconductor by FRAP Microscopy.

Tailoring the photoluminescence (PL) of semiconductors through spatiotemporal manipulation of dynamics of photoexcited carriers is of paramount importance for understanding the emitting mechanism and developing high‐performance devices. Herein, fluorescence recovery after photobleaching (FRAP) microscopy, a powerful tool in biology, is first utilized to simultaneously manipulate and monitor the dynamics of photoexcited carrier in attractive 2D transition metal dichalcogenide monolayers (1L‐TMDs). This allows on‐demand access to the PL dark state of 1L‐TMDs, based on the triggered exciton–exciton annihilation by pump beam‐initiated photodoping. Using a 0.7‐µm‐diametered pump laser, the PL dark region can be facilely tailored from ≈0.5 to ≈5 µm over a 10‐µm‐1L‐WS2 flake. An interesting photoinduced dedoping effect in 1L‐TMDs after photodoping is discovered by FRAP, which has not been observed before and might account for the non‐blinking emission of 1L‐TMDs. The revealed mono‐exponential photo‐dedoping can also be kinetically tailored by ≈170‐fold (k: 0.11–19.00 s‐1) by humidity, power of incident laser and type of 1L‐TMDs. This study demonstrates the power of FRAP microscopy in exploring the effect of photoexcited carrier dynamics on the PL property of semiconductors, holding promises for understanding light‐emitting mechanism and optimizing operational parameters for optoelectronic devices. [ABSTRACT FROM AUTHOR]