Free carrier generation and recombination in polymer-wrapped semiconducting carbon nanotube films and heterojunctions

Dominick J. Bindl, Andrew J. Ferguson, Meng Yin Wu, Nikos Kopidakis, Jeffrey L. Blackburn*, Michael S. Arnold

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)

Abstract

Semiconducting single-walled carbon nanotubes (s-SWCNTs) are promising for solution-processed, thin film photovoltaics due to their strong near-infrared absorptivity and excellent transport properties. We report on the generation yield and recombination kinetics of free charge carriers in photoexcited thin films of polymer-wrapped s-SWCNTs with and without an overlying electron-accepting C60 layer, using time-resolved microwave photoconductivity (TRMC). Free carriers are generated in neat s-SWCNT films, even without an obvious driving force for exciton dissociation. However, most carriers recombine in <10 ns. Adding C60 increases the yield and extends the lifetime of a significant fraction of free carriers to ≫100 ns via interfacial charge separation. Spectral dependencies indicate that the driving force for interfacial electron transfer vanishes for large-diameter SWCNTs, from which we approximate (9,7) s-SWCNT energetics. We estimate a free carrier generation yield of ∼6% in neat s-SWCNT films and 9 GHz SWCNT hole mobility of >1.3 cm2 V-1 s-1. These studies improve understanding of s-SWCNT photoresponses in solar cells and photodetectors.

Original languageEnglish
Pages (from-to)3550-3559
Number of pages10
JournalJournal of Physical Chemistry Letters
Volume4
Issue number21
DOIs
Publication statusPublished - 7 Nov 2013
Externally publishedYes

Keywords

  • C
  • exciton
  • fullerene
  • lifetime
  • near-infrared
  • photovoltaic
  • time-resolved microwave conductivity

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