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Filling Exciton Trap-States in Two-Dimensional Tungsten Disulfide (WS₂) and Diselenide (WSe₂) Monolayers.

ABSTRACT: Two-dimensional transition metal dichalcogenides (2D-TMDs) hold a great potential to platform future flexible optoelectronics. The beating hearts of these materials are their excitons known as X_A and X_B, which arise from transitions between spin-orbit split (SOS) levels in the conduction and valence bands at the K-point. The functionality of 2D-TMD-based devices is determined by the dynamics of these excitons. One of the most consequential channels of exciton decay on the device functionality is the defect-assisted recombination (DAR). Here, we employ steady-state absorption and emission spectroscopies, and pump density-dependent femtosecond transient absorption spectroscopy to report on the effect of DAR on the lifetime of excitons in monolayers of tungsten disulfide (2D-WS₂) and diselenide (2D-WSe₂). These pump-probe measurements suggested that while exciton decay dynamics in both monolayers are driven by DAR, in 2D-WS₂, defect states near the X_B exciton fill up before those near the X_A exciton. However, in the 2D-WSe₂ monolayer, the defect states fill up similarly. Understanding the contribution of DAR on the lifetime of excitons and the partition of this decay channel between X_A and X_B excitons may open new horizons for the incorporation of 2D-TMD materials in future optoelectronics.

SUBMITTER: Ezgi Eroglu Z

PROVIDER: S-EPMC8002918 | biostudies-literature |

REPOSITORIES: biostudies-literature

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