Different orientation of the transition dipole moments of two similar Pt(II) complexes and their potential for high efficiency organic light-emitting diodes

Christian Mayr, Masatsugu Taneda, Chihaya Adachi, Wolfgang Brütting

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

The efficiency of organic light-emitting diodes (OLEDs) is especially limited by their low light outcoupling efficiency. An approach for its enhancement is the use of horizontally oriented emitter molecules with respect to the substrate. In this study we quantitatively determine the orientation of the optical transition dipole moments in doped films of two similar phosphorescent Pt(II) complexes having a linear molecular structure. These emitters are employed in OLED devices and their efficiency is analyzed by optical simulations. For an OLED with slightly more horizontally oriented emitter molecules an external quantum efficiency (ηEQE) of 15.8% at low current-density is realized, indicating a relative improvement of outcoupling efficiency of 5.3% compared to the isotropic case. However, a very similar complex adopting isotropic molecular orientation yields ηEQEof only 11.5% implying an imperfect charge carrier balance in the OLED device and a shift of the recombination zone. Furthermore, we highlight the enormous potential of horizontal molecular orientation of emitting molecules in OLEDs.

Original languageEnglish
Pages (from-to)3031-3037
Number of pages7
JournalOrganic Electronics
Volume15
Issue number11
DOIs
Publication statusPublished - Nov 2014

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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