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Title: Photoluminescence Dynamics of Aryl sp 3 Defect States in Single-Walled Carbon Nanotubes

Photoluminescent defect states introduced by sp 3 functionalization of semiconducting carbon nanotubes are rapidly emerging as important routes for boosting emission quantum yields and introducing new functionality. Knowledge of the relaxation dynamics of these states is required for understanding how functionalizing agents (molecular dopants) may be designed to access specific behaviors. We measure photoluminescence (PL) decay dynamics of sp 3 defect states introduced by aryl functionalization of the carbon nanotube surface. Results are given for five different nanotube chiralities, each doped with a range of aryl functionality. We find the PL decays of these sp 3 defect states are biexponential, with both components relaxing on timescales of ~ 100 ps. Exciton trapping at defects is found to increases PL lifetimes by a factor of 5-10, in comparison to those for the free exciton. A significant chirality dependence is observed in the decay times, ranging from 77 ps for (7,5) nanotubes to > 600 ps for (5,4) structures. The strong correlation of time constants with emission energy indicates relaxation occurs via multiphonon decay processes, with close agreement to theoretical expectations. Variation of the aryl dopant further modulates decay times by 10-15%. The aryl defects also affect PL lifetimes of the freemore » E 11 exciton. Shortening of the E 11 bright state lifetime as defect density increases provides further confirmation that defects act as exciton traps. A similar shortening of the E11 dark exciton lifetime is found as defect density increases, providing strong experimental evidence that dark excitons are also trapped at such defect sites.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [2] ;  [1] ;  [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Univ. of Maryland, College Park, MD (United States)
Publication Date:
Report Number(s):
LA-UR-17-24661
Journal ID: ISSN 1936-0851
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 9; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; Carbon nanotubes; diazonium salts; doping; exciton localization; photoluminescence; time-correlated single-photon counting
OSTI Identifier:
1375887

Hartmann, Nicolai F., Velizhanin, Kirill A., Haroz, Erik H., Kim, Mijin, Ma, Xuedan, Wang, YuHuang, Htoon, Han, and Doorn, Stephen K.. Photoluminescence Dynamics of Aryl sp 3 Defect States in Single-Walled Carbon Nanotubes. United States: N. p., Web. doi:10.1021/acsnano.6b02986.
Hartmann, Nicolai F., Velizhanin, Kirill A., Haroz, Erik H., Kim, Mijin, Ma, Xuedan, Wang, YuHuang, Htoon, Han, & Doorn, Stephen K.. Photoluminescence Dynamics of Aryl sp 3 Defect States in Single-Walled Carbon Nanotubes. United States. doi:10.1021/acsnano.6b02986.
Hartmann, Nicolai F., Velizhanin, Kirill A., Haroz, Erik H., Kim, Mijin, Ma, Xuedan, Wang, YuHuang, Htoon, Han, and Doorn, Stephen K.. 2016. "Photoluminescence Dynamics of Aryl sp 3 Defect States in Single-Walled Carbon Nanotubes". United States. doi:10.1021/acsnano.6b02986. https://www.osti.gov/servlets/purl/1375887.
@article{osti_1375887,
title = {Photoluminescence Dynamics of Aryl sp 3 Defect States in Single-Walled Carbon Nanotubes},
author = {Hartmann, Nicolai F. and Velizhanin, Kirill A. and Haroz, Erik H. and Kim, Mijin and Ma, Xuedan and Wang, YuHuang and Htoon, Han and Doorn, Stephen K.},
abstractNote = {Photoluminescent defect states introduced by sp3 functionalization of semiconducting carbon nanotubes are rapidly emerging as important routes for boosting emission quantum yields and introducing new functionality. Knowledge of the relaxation dynamics of these states is required for understanding how functionalizing agents (molecular dopants) may be designed to access specific behaviors. We measure photoluminescence (PL) decay dynamics of sp3 defect states introduced by aryl functionalization of the carbon nanotube surface. Results are given for five different nanotube chiralities, each doped with a range of aryl functionality. We find the PL decays of these sp3 defect states are biexponential, with both components relaxing on timescales of ~ 100 ps. Exciton trapping at defects is found to increases PL lifetimes by a factor of 5-10, in comparison to those for the free exciton. A significant chirality dependence is observed in the decay times, ranging from 77 ps for (7,5) nanotubes to > 600 ps for (5,4) structures. The strong correlation of time constants with emission energy indicates relaxation occurs via multiphonon decay processes, with close agreement to theoretical expectations. Variation of the aryl dopant further modulates decay times by 10-15%. The aryl defects also affect PL lifetimes of the free E11 exciton. Shortening of the E11 bright state lifetime as defect density increases provides further confirmation that defects act as exciton traps. A similar shortening of the E11 dark exciton lifetime is found as defect density increases, providing strong experimental evidence that dark excitons are also trapped at such defect sites.},
doi = {10.1021/acsnano.6b02986},
journal = {ACS Nano},
number = 9,
volume = 10,
place = {United States},
year = {2016},
month = {8}
}