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Proceedings Paper

Effects of local environment on the ultra-fast carrier dynamics of photo-excited 2D transition metal dichalcogenides
Author(s): Jeremy R. Dunklin; Hanyu Zhang; Elisa M. Miller; Jao van de Lagemaat
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Paper Abstract

Layered transition metal dichalcogenides (TMDs) represent a diverse, emerging source of two-dimensional (2D) nanostructures with broad application in optoelectronics and energy. In particular, tungsten disulfide (WS2) is an efficient visible light absorber with relatively high carrier mobilities and catalytic activity towards hydrogen evolution. While explanation of the quantum confinement and excitonic effects governing TMD optoelectronic properties has progressed in recent years, less is known about the ultra-fast photoresponse and carrier dynamics following light excitation. This work utilizes transient absorption spectroscopy, with pump tunability and broadband visible probing, to monitor the carrier dynamics of both CVD-grown monolayer and solution exfoliated WS2. Picosecond-scale features include simultaneous bleaching of excitonic states and a red-shifted absorption spectrum attributed to bandgap renormalization, while free carriers, defect trapped carriers, and recombination signatures are apparent at increasing pico- to nanosecond lifetimes. Features associated with excitons, trions, and photo-excited carriers exhibit strong dependence on local environmental factors. Moisture, oxygen, chemical dopants, and dielectric environment strongly affect the strength and decay lifetimes of these photo-excited species. These results highlight the importance of understanding and controlling these local environmental factors to the rational design and implementation of 2D TMDs optoelectronic device platforms.

Paper Details

Date Published: 7 September 2018
PDF: 9 pages
Proc. SPIE 10724, Physical Chemistry of Semiconductor Materials and Interfaces XVII, 1072412 (7 September 2018); doi: 10.1117/12.2321308
Show Author Affiliations
Jeremy R. Dunklin, National Renewable Energy Lab. (United States)
Hanyu Zhang, National Renewable Energy Lab. (United States)
Elisa M. Miller, National Renewable Energy Lab. (United States)
Jao van de Lagemaat, National Renewable Energy Lab. (United States)

Published in SPIE Proceedings Vol. 10724:
Physical Chemistry of Semiconductor Materials and Interfaces XVII
Hugo A. Bronstein; Felix Deschler, Editor(s)

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