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Filling Exciton Trap-States in Two-Dimensional Tungsten Disulfide (WS2) and Diselenide (WSe2) Monolayers
Zeynep Ezgi Eroglu1, Dillon Contreras1, Pouya Bahrami1
1Department of Chemistry & Biochemistry, California State University, Northridge, 18111 Nordhoff Street, Northridge, CA 91330, USA.
Defect-assisted recombination (DAR) impacts exciton lifetimes in two-dimensional transition metal dichalcogenides (2D-TMDs). In WS2, DAR affects XB excitons before XA, while WSe2 shows similar defect filling for both.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Optoelectronics
Background:
- Two-dimensional transition metal dichalcogenides (2D-TMDs) are promising for flexible optoelectronics.
- Excitons (XA, XB) are crucial for 2D-TMD device functionality.
- Defect-assisted recombination (DAR) is a key exciton decay pathway.
Purpose of the Study:
- Investigate the effect of DAR on exciton lifetimes in 2D-WS2 and 2D-WSe2 monolayers.
- Determine how DAR impacts XA and XB excitons differently in these materials.
Main Methods:
- Steady-state absorption and emission spectroscopies.
- Pump density-dependent femtosecond transient absorption spectroscopy.
- Comparative analysis of 2D-WS2 and 2D-WSe2 monolayers.
Main Results:
- Exciton decay in both 2D-WS2 and 2D-WSe2 is primarily driven by DAR.
- In 2D-WS2, defect states near XB fill before those near XA.
- In 2D-WSe2, defect states fill similarly for both XA and XB excitons.
Conclusions:
- DAR significantly influences exciton lifetimes in 2D-TMDs.
- Understanding DAR's role in partitioning decay between XA and XB is vital for optoelectronic applications.
- This research paves the way for advanced 2D-TMD material design.
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