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On Optical Dipole Moment and Radiative Recombination Lifetime of Excitons in WSe 2
Author(s) -
Jin Chenhao,
Kim Jonghwan,
Wu Kedi,
Chen Bin,
Barnard Edward S.,
Suh Joonki,
Shi Zhiwen,
Drapcho Steven G.,
Wu Junqiao,
Schuck Peter James,
Tongay Sefaattin,
Wang Feng
Publication year - 2017
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201601741
Subject(s) - exciton , photoluminescence , radiative transfer , dipole , spontaneous emission , delocalized electron , materials science , transition dipole moment , monolayer , atomic physics , physics , molecular physics , condensed matter physics , optoelectronics , optics , nanotechnology , laser , quantum mechanics
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 WSe 2 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 WSe 2 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 WSe 2 from the absorption measurements. In addition, the “effective” radiative lifetime in WSe 2 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 WSe 2 .