Photorefractive conjugated polymer-liquid crystal composites

Michael R Wasielewski*, B. A. Yoon, M. Fuller, G. P. Wiederrecht, M. P. Niemczyk, W. A. Svec

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations


A new mechanism for space-charge field formation in photorefractive liquid crystal composites containing poly(2,5-bis(2′-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) and the electron acceptor N,N′-dioctyl-1,4:5,8-naphthalenediimide, NI, is observed. Using asymmetric energy transfer (beam coupling) measurements that are diagnostic for the photorefractive effect, the direction of beam coupling as a function of grating fringe spacing inverts at a spacing of 5.5 μm. We show that the inversion is due to a change in the dominant mechanism for space-charge field formation. At small fringe spacings, the space-charge field is formed by ion diffusion in which the photogenerated anion is the more mobile species. At larger fringe spacings, the polarity of the space charge field inverts due to dominance of a charge transport mechanism in which photogenerated holes are the most mobile species due to hole migration along the BEH-PPV chains coupled with interchain hole hopping. Control experiments are presented, which use composites that can access only one of the two charge transport mechanisms. The results show that charge migration over long distances leading to enhanced photorefractive effects can be obtained using conjugated polymers dissolved in liquid crystals.

Original languageEnglish (US)
Pages (from-to)211-219
Number of pages9
JournalMaterials Research Society Symposium - Proceedings
StatePublished - Dec 1 2000
EventThin Films for Optical Waveguide Devices and Materials for Optical Limiting - Boston, MA, USA
Duration: Nov 30 1999Dec 3 1999

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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