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

Abstract

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.

In Situ Optical Imaging-Enabled New Insights into Nanoscale Photofunctional Materials: Visualization, Manipulation, and Beyond

“…Recently, Wang and co-workers utilized a wide-field FRAP microscope to visually tailor the FL dark state of a three-atom-thick 2D monolayer transition metal dichalcogenide (1L-TMD) via optical manipulation of local charge carrier density . Although FRAP (fluorescence recovery after photobleaching) microscopy has been widely used to investigate the mobility of fluorophore-labeled biomolecules in the field of biology, − they first demonstrated its power in visually manipulating the carrier dynamics of 2D semiconductors.…”

“…Pale red arrow represents the weakly emissive process. Reproduced with permission from ref . Copyright 2022 Wiley-VCH GmbH.…”

“…Recently, Wang and co-workers utilized a wide-field FRAP microscope to visually tailor the FL dark state of a threeatom-thick 2D monolayer transition metal dichalcogenide (1L-TMD) via optical manipulation of local charge carrier density. 50 Although FRAP (fluorescence recovery after photobleaching) microscopy has been widely used to investigate the mobility of fluorophore-labeled biomolecules in the field of biology, 51−53 they first demonstrated its power in visually manipulating the carrier dynamics of 2D semiconductors. As shown in Figure 9A, a tightly focused high-intensity 405 nm laser (with a spot size of ∼0.7 μm and a pulse width of 3−30 ms) is used as a pump beam to instantaneously inject abundant excitons into a 1L-TMD flake, and another low-intensity 488 nm probe laser (with a spot size of ∼100 μm, ∼5 W cm −2 ) is used to continuously monitor the following FL evolution.…”

Self‐Healing Ability of Perovskites Observed via Photoluminescence Response on Nanoscale Local Forces and Mechanical Damage

“…[21,22] Recently, photoassisted PL recovery after bleaching was also observed in monolayer transition metal dichalcogenide (1L-WS 2 ) materials. [23] MHP micro-and nanocrystals exhibit pronounced PL blinking and flickering. [24][25][26][27][28][29][30][31] When comparing classical semiconductor quantum dots [21,32] with MHPs we note that PL blinking and flickering is not only observed in MHP nanocrystals, [33] but also in sub-micrometer crystals, grains in thin films and even in micrometer-sized objects.…”

“…[ 21 , 22 ] Recently, photoassisted PL recovery after bleaching was also observed in monolayer transition metal dichalcogenide (1L‐WS 2 ) materials. [ 23 ]…”