Increased light outcoupling efficiency in dye-doped small molecule organic light-emitting diodes with horizontally oriented emitters

Jörg Frischeisen, Daisuke Yokoyama, Ayataka Endo, Chihaya Adachi, Wolfgang Brütting

Research output: Contribution to journalArticlepeer-review

157 Citations (Scopus)

Abstract

Small molecule organic light-emitting diodes (SM-OLEDs) are efficient large area light sources facing their market entry. However, a low light outcoupling efficiency of typically 20% still strongly limits device performance. Here, we highlight the potential of employing dye-doped emission layers with emitting molecules having horizontally oriented transition dipole moments. The effect of molecular orientation is explained by studying optical simulations that distinguish between horizontal and vertical dipole orientation. In addition, an experimental method that enables straightforward determination of dipole orientation in guest-host systems is presented and used for the analysis of two materials that are very similar except for their orientation. By measuring the external electroluminescence quantum efficiency of SM-OLEDs based on these materials, evidence is found that a mainly horizontal dipole orientation enhances light outcoupling by around 45%. Furthermore, the effect of orientation in SM-OLEDs offers many additional benefits concerning stack design and has fundamental implications for material choice.

Original languageEnglish
Pages (from-to)809-817
Number of pages9
JournalOrganic Electronics
Volume12
Issue number5
DOIs
Publication statusPublished - May 2011

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

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