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Title: Unexpectedly Fast Phonon-Assisted Exciton Hopping between Carbon Nanotubes

Carbon-nanotube (CNT) aggregates are promising light-absorbing materials for photovoltaics. The hopping rate of excitons between CNTs directly affects the efficiency of these devices. We theoretically investigate phonon-assisted exciton hopping, where excitons scatter with phonons into a same-tube transition state, followed by intertube Coulomb scattering into the final state. Second-order hopping between bright excitonic states is as fast as the first-order process (~1 ps). For perpendicular CNTs, the high rate stems from the high density of phononic states; for parallel CNTs, the reason lies in relaxed selection rules. Moreover, second-order exciton transfer between dark and bright states, facilitated by phonons with large angular momentum, has rates comparable to bright-to-bright transfer, so dark excitons provide an additional pathway for energy transfer in CNT composites. Furthermore, as dark excitons are difficult to probe in experiment, predictive theory is critical for understanding exciton dynamics in CNT composites.
Authors:
 [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [1]
  1. Univ. of Wisconsin-Madison, Madison, WI (United States)
Publication Date:
Grant/Contract Number:
SC0008712
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 121; Journal Issue: 24; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Research Org:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY
OSTI Identifier:
1434268

Davoody, A. H., Karimi, F., Arnold, M. S., and Knezevic, I.. Unexpectedly Fast Phonon-Assisted Exciton Hopping between Carbon Nanotubes. United States: N. p., Web. doi:10.1021/acs.jpcc.7b03994.
Davoody, A. H., Karimi, F., Arnold, M. S., & Knezevic, I.. Unexpectedly Fast Phonon-Assisted Exciton Hopping between Carbon Nanotubes. United States. doi:10.1021/acs.jpcc.7b03994.
Davoody, A. H., Karimi, F., Arnold, M. S., and Knezevic, I.. 2017. "Unexpectedly Fast Phonon-Assisted Exciton Hopping between Carbon Nanotubes". United States. doi:10.1021/acs.jpcc.7b03994. https://www.osti.gov/servlets/purl/1434268.
@article{osti_1434268,
title = {Unexpectedly Fast Phonon-Assisted Exciton Hopping between Carbon Nanotubes},
author = {Davoody, A. H. and Karimi, F. and Arnold, M. S. and Knezevic, I.},
abstractNote = {Carbon-nanotube (CNT) aggregates are promising light-absorbing materials for photovoltaics. The hopping rate of excitons between CNTs directly affects the efficiency of these devices. We theoretically investigate phonon-assisted exciton hopping, where excitons scatter with phonons into a same-tube transition state, followed by intertube Coulomb scattering into the final state. Second-order hopping between bright excitonic states is as fast as the first-order process (~1 ps). For perpendicular CNTs, the high rate stems from the high density of phononic states; for parallel CNTs, the reason lies in relaxed selection rules. Moreover, second-order exciton transfer between dark and bright states, facilitated by phonons with large angular momentum, has rates comparable to bright-to-bright transfer, so dark excitons provide an additional pathway for energy transfer in CNT composites. Furthermore, as dark excitons are difficult to probe in experiment, predictive theory is critical for understanding exciton dynamics in CNT composites.},
doi = {10.1021/acs.jpcc.7b03994},
journal = {Journal of Physical Chemistry. C},
number = 24,
volume = 121,
place = {United States},
year = {2017},
month = {6}
}