Effect of acceptor lamination on photocarrier dynamics in hole transporting hexabenzocoronene nanotubular self-assembly

Yusuke Wakikawa, Tadaaki Ikoma, Yohei Yamamoto, Takanori Fukushima, Takuzo Aida, Kimio Akiyama

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Measurements of transient photoconductance under an external magnetic field were used to investigate photocarrier dynamics in low-dimensional hexabenzocoronene (HBC) self-assemblies, which are a promising material group for highly efficient solar cells achieved by bottom-up technology, and to clarify the effect of lamination with electron acceptor layer on the surfaces of HBC nanotubes. In an HBC column without an acceptor, the carrier generation yield from a geminate electron-hole (e-h) pair is dependent on the external electric and magnetic fields. The time dependence of the magnetic field effect on geminate e-h pair dynamics in the HBC column structure was analyzed to estimate the recombination rate constants of the singlet and triplet e-h pairs (krS and krT), which were 1.5 × 108 and 1.2 × 108 s-1 respectively. The same kinetic analysis with consideration of the electric field effect on the photocarrier generation yield provided an electric field dependent dissociation rate constant in the range of 107-10 8 s-1 in the HBC column structure. However, neither electric nor magnetic field effects on the carrier generation process were observed in acceptor-appended HBC nanotubes. The disappearance of the external field effects in acceptor-appended HBC indicates that the geminate recombination is reduced substantially by a well-organized donor/acceptor heterojunction with an interval of a few nanometers due to some σ-bonds. However, efficient nongeminate recombination with a ratio of krS:k rT = 1.0:0.8 in the acceptor-appended HBC nanotubes was also elucidated by the incident photon density and magnetic field effects, which is an inherent nature in materials with high carrier density.

Original languageEnglish
Pages (from-to)15295-15305
Number of pages11
JournalJournal of Physical Chemistry C
Volume117
Issue number29
DOIs
Publication statusPublished - 2013 Jul 25

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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