Ultrafast conductivity in a low-band-gap polyphenylene and fullerene blend studied by terahertz spectroscopy

Hynek Nemec, Han-Kwang Nienhuys, Erik Perzon, Fengling Zhang, Olle Inganas, Petr Kuzel, Villy Sundström

Research output: Contribution to journalArticlepeer-review

28 Citations (SciVal)

Abstract

Time-resolved terahertz spectroscopy and Monte Carlo simulations of charge-carrier motion are used to investigate photoinduced transient conductivity in a blend of a low-band-gap polyphenylene copolymer and fullerene derivative. The optical excitation pulse generates free holes delocalized on polymer chains. We show that these holes exhibit a very high initial mobility as their initial excess energy facilitates their transport over defects (potential barriers) on polymer chains. The conductivity then drops down rapidly within 1 ps, and we demonstrate that this decrease occurs essentially by two mechanisms. First, the carriers loose their excess energy and they thus become progressively localized between the on-chain potential barriers-this results in a mobility decay with a rate of (180 fs)(-1). Second, carriers are trapped at defects (potential wells) with a capture rate of (860 fs)(-1). At longer time scales, populations of mobile and trapped holes reach a quasiequilibrium state and further conductivity decrease becomes very slow.</p>.
Original languageEnglish
JournalPhysical Review B (Condensed Matter and Materials Physics)
Volume79
Issue number24
DOIs
Publication statusPublished - 2009

Bibliographical note

The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Chemical Physics (S) (011001060)

Subject classification (UKÄ)

  • Atom and Molecular Physics and Optics

Keywords

  • polymer blends
  • photoconductivity
  • Monte Carlo methods
  • hole mobility
  • energy gap
  • fullerenes
  • terahertz wave spectra
  • time
  • resolved spectra

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