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Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time- resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond timescale after the excitation. As proof of principle, we extract the interlayer exciton formation time 0.4 ps at 160 μJ/cm2 fluence in a MoS2/MoSe2 heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Dark excitons, ultrafast photocurrent, MoS2/MoSe2

Date published: 2023-10-25

Publisher: American Chemical Society (ACS)

Journal:

• Nano Letters (ISSN: 15306984) vol. 23 issue. 20 p. 9212-9218

Funding:

• Bundesministerium für Bildung und Forschung 05K22KE3
• Deutsche Forschungsgemeinschaft TRR227 B08

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1021/acs.nanolett.3c01708

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Updated at: 2025-02-14 16:31:00 +0900

Published on MDR: 2025-02-14 16:31:00 +0900