Charge-recombination processes in oligomer- and polymer-based light-emitting diodes: A molecular picture

David Beljonne*, Zhigang Shuai, Aijun Ye, Jean-Luc Bredas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

An overview of our recent work on the mechanisms of singlet and triplet exciton formation in electroluminescent π-conjugated materials will be presented. According to simple spin statistics, only one-fourth of the excitons are formed as singlets. However, deviations from that statistics can occur if the initially formed triplet charge-transfer (CT) excited states are amenable to intersystem crossing or dissociation. Although the electronic couplings between the CT states and the neutral exciton states are expected to be largest for the lowest singlet and triplet excitons (S1 and T1, respectively), the possibility for direct recombination into T1 is always very small due to the large exchange energy. In small molecules, spin statistics is expected to be observed because both singlet and triplet exciton formations proceed via higher-lying Sn/Tn states with similar electronic couplings and fast formation rates. In extended conjugated chains, however, that the 1CT → S1 pathway is faster while the 3CT→ Tn channels become much slower, opening the route to intersystem crossing or dissociation among the 3CT states.

Original languageEnglish (US)
Pages (from-to)419-427
Number of pages9
JournalJournal of the Society for Information Display
Volume13
Issue number5
DOIs
StatePublished - May 1 2005

Keywords

  • Charge recombination
  • Charge transfer
  • Intersystem crossing
  • Organic light-emitting diodes
  • Polymer light-emitting diodes
  • Singlet and triplet excitons

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

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