Morphology and charge transport in poly(2-methoxy-5-(2 '-ethylhexyloxy)-1,4-phenylenevinylene) films

U Jeng, C H Hsu, H S Sheu, H.Y. Lee, A R Inigo, H C Chiu, W S Fann, S H Chen, A C Su, T L Lin, K.Y. Peng, S A Chen

Research output: Contribution to journalArticlepeer-review

55 Citations (Scopus)

Abstract

Structural characteristics of optical quality poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) films drop-cast from toluene solutions have been examined by use of wide-angle (WAXS) and small-angle X-ray scattering (SAXS) as well as field-emission scanning electron microscopy. For the as-cast film SAXS and WAXS patterns clearly suggest existence of nanodomains of mesomorphic order. Under grazing incidence, both SAXS and WAXS patterns of the as-cast film exhibit impressive uniaxial symmetry with strong scattering along the film normal; however, the corresponding normal-incidence patterns are circularly isotropic, implying in-plane random orientation. A structural model consisting of preferentially uniaxial-oriented nanodomains and disordered matrix is therefore proposed for the as-cast film. Annealing at 210 degrees C results in disorientation of nanodomains: this decrease in structural asymmetry upon heat treatment correlates well with concomitant changes in charge transport behavior determined from time-of-flight measurements, manifesting dramatically decreased charge mobility as well as transition from nondispersive to dispersive modes.

Original languageEnglish
Pages (from-to)6566-6574
Number of pages9
JournalMacromolecules
Volume38
Issue number15
Early online date30 Jun 2005
DOIs
Publication statusPublished - 26 Jul 2005

Keywords

  • structural characterisitcs
  • morphology
  • X-ray scattering
  • charge transport

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