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Title: Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport

Abstract

Single-walled carbon nanotubes (SWCNTs) have potential to act as light-harvesting elements in thin film photovoltaic devices, but performance is in part limited by the efficiency of exciton diffusion processes within the films. Factors contributing to exciton transport can include film morphology encompassing nanotube orientation, connectivity, and interaction geometry. Such factors are often defined by nanotube surface structures that are not yet well understood. We present the results of a combined pump-probe and photoluminescence imaging study of polyfluorene (PFO)-wrapped (6,5) and (7,5) SWCNTs that provide additional insight into the role played by polymer structures in defining exciton transport. The pump-probe measurements suggest exciton transport occurs over larger length scales in films composed of PFO-wrapped (7,5) SWCNTs, compared to those prepared from PFO-bpy-wrapped (6,5) SWCNTs. To explore the role the difference in polymer structure may play as a possible origin of differing transport behaviors, we performed a photoluminescence imaging study of individual polymer-wrapped (6,5) and (7,5) SWCNTs. The PFO-bpy-wrapped (6,5) SWCNTs showed more uniform intensity distributions along their lengths, in contrast to the PFO-wrapped (7,5) SWCNTs, which showed irregular, discontinuous intensity distributions. These differences likely originate from differences in surface coverage and suggest the PFO wrapping on (7,5) nanotubes produces a moremore » open surface structure than is available with the PFO-bpy wrapping of (6,5) nanotubes. Furthermore, the open structure likely leads to improved intertube coupling that enhances exciton transport within the (7,5) films, consistent with the results of our pump-probe measurements.« less

Authors:
 [1];  [1];  [2];  [2];  [2]; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Integrated Nanotechnologies
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1343088
Alternate Identifier(s):
OSTI ID: 1361483
Report Number(s):
NREL/JA-5900-67896; LA-UR-16-29016
Journal ID: ISSN 1936-0851
Grant/Contract Number:  
AC36-08GO28308; AC52-06NA25396
Resource Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 12; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 77 NANOSCIENCE AND NANOTECHNOLOGY; carbon nanotubes; energy harvesting; exciton transport; photovoltaics; surface structure; Material Science

Citation Formats

Hartmann, Nicolai F., Pramanik, Rajib, Dowgiallo, Anne-Marie, Ihly, Rachelle, Blackburn, Jeffrey L., and Doorn, Stephen K. Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport. United States: N. p., 2016. Web. doi:10.1021/acsnano.6b07168.
Hartmann, Nicolai F., Pramanik, Rajib, Dowgiallo, Anne-Marie, Ihly, Rachelle, Blackburn, Jeffrey L., & Doorn, Stephen K. Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport. United States. doi:10.1021/acsnano.6b07168.
Hartmann, Nicolai F., Pramanik, Rajib, Dowgiallo, Anne-Marie, Ihly, Rachelle, Blackburn, Jeffrey L., and Doorn, Stephen K. Tue . "Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport". United States. doi:10.1021/acsnano.6b07168. https://www.osti.gov/servlets/purl/1343088.
@article{osti_1343088,
title = {Photoluminescence Imaging of Polyfluorene Surface Structures on Semiconducting Carbon Nanotubes: Implications for Thin Film Exciton Transport},
author = {Hartmann, Nicolai F. and Pramanik, Rajib and Dowgiallo, Anne-Marie and Ihly, Rachelle and Blackburn, Jeffrey L. and Doorn, Stephen K.},
abstractNote = {Single-walled carbon nanotubes (SWCNTs) have potential to act as light-harvesting elements in thin film photovoltaic devices, but performance is in part limited by the efficiency of exciton diffusion processes within the films. Factors contributing to exciton transport can include film morphology encompassing nanotube orientation, connectivity, and interaction geometry. Such factors are often defined by nanotube surface structures that are not yet well understood. We present the results of a combined pump-probe and photoluminescence imaging study of polyfluorene (PFO)-wrapped (6,5) and (7,5) SWCNTs that provide additional insight into the role played by polymer structures in defining exciton transport. The pump-probe measurements suggest exciton transport occurs over larger length scales in films composed of PFO-wrapped (7,5) SWCNTs, compared to those prepared from PFO-bpy-wrapped (6,5) SWCNTs. To explore the role the difference in polymer structure may play as a possible origin of differing transport behaviors, we performed a photoluminescence imaging study of individual polymer-wrapped (6,5) and (7,5) SWCNTs. The PFO-bpy-wrapped (6,5) SWCNTs showed more uniform intensity distributions along their lengths, in contrast to the PFO-wrapped (7,5) SWCNTs, which showed irregular, discontinuous intensity distributions. These differences likely originate from differences in surface coverage and suggest the PFO wrapping on (7,5) nanotubes produces a more open surface structure than is available with the PFO-bpy wrapping of (6,5) nanotubes. Furthermore, the open structure likely leads to improved intertube coupling that enhances exciton transport within the (7,5) films, consistent with the results of our pump-probe measurements.},
doi = {10.1021/acsnano.6b07168},
journal = {ACS Nano},
number = 12,
volume = 10,
place = {United States},
year = {2016},
month = {12}
}

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Figures / Tables:

Figure 1 Figure 1: (a) Molecular structures of the polyfluorene polymers PFO-bpy (left) and PFO (right). (b) Absorbance of (6,5)/PFO-bpy sample, with PL spectrum (dotted trace) obtained for E22 excitation at 570 nm. (c) Absorbance of (7,5)/PFO sample, with PL spectrum (dotted trace) obtained for E22 excitation at 650 nm. (d) PLEmore » map of (6,5)/PFO-bpy sample. (e) PLE map of (7,5)/PFO sample.« less

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Works referencing / citing this record:

Performance improvement induced by asymmetric Y 2 O 3 -coated device structure to carbon-nanotube-film based photodetectors
journal, November 2017

  • Wang, Fanglin; Xu, Haitao; Huang, Huixin
  • Applied Physics Letters, Vol. 111, Issue 19
  • DOI: 10.1063/1.5003980

    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.