On Optical Dipole Moment and Radiative Recombination Lifetime of Excitons in WSe2

Chenhao Jin, Jonghwan Kim, Kedi Wu, Bin Chen, Edward S. Barnard, Joonki Suh, Zhiwen Shi, Steven G. Drapcho, Junqiao Wu, Peter James Schuck, Sefaattin Tongay, Feng Wang

Research output: Contribution to journalArticle

13 Scopus citations

Abstract

Optical dipole moment is the key parameter of optical transitions, as it directly determines the strength of light–matter interaction such as intrinsic radiative lifetime. However, experimental determination of these fundamental properties of excitons in monolayer WSe2 is largely limited, because the commonly used measurement, such as (time-resolved) photoluminescence, is inherently difficult to probe the intrinsic properties. For example, dark states below bright exciton can change the photoluminescence emission rate by orders of magnitude and gives an “effective” radiative lifetime distinctive from the intrinsic one. On the other hand, such “effective” radiative lifetime becomes important itself because it describes how dark states affect exciton dynamics. Unfortunately, the “effective” radiative lifetime in monolayer WSe2 is also not determined as it requires photoluminescence measurement with resonant excitation, which is technically difficult. These difficulties are overcome here to obtain both the “intrinsic” and “effective” radiative lifetime experimentally. A framework is developed to determine the dipole moment and “intrinsic” radiative lifetime of delocalized excitons in monolayer WSe2 from the absorption measurements. In addition, the “effective” radiative lifetime in WSe2 is obtained through time-resolved photoluminescence and absolute quantum-yield measurement at resonant excitation. These results provide helpful information for fundamental understanding of exciton light–matter interaction in WSe2.

Original languageEnglish (US)
Article number1601741
JournalAdvanced Functional Materials
Volume27
Issue number19
DOIs
StatePublished - May 18 2017

Keywords

  • WSe
  • dark states
  • delocalized excitons
  • dipole moments
  • radiative lifetimes

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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    Jin, C., Kim, J., Wu, K., Chen, B., Barnard, E. S., Suh, J., Shi, Z., Drapcho, S. G., Wu, J., Schuck, P. J., Tongay, S., & Wang, F. (2017). On Optical Dipole Moment and Radiative Recombination Lifetime of Excitons in WSe2 Advanced Functional Materials, 27(19), [1601741]. https://doi.org/10.1002/adfm.201601741