White top-emitting organic light-emitting diodes with solution-processed nano-particle scattering layers

Tim Schaefer, Tobias Schwab, Simone Lenk, Malte Christian Gather

Research output: Contribution to journalLetterpeer-review

8 Citations (Scopus)

Abstract

A random scattering approach to enhance light extraction in white top-emitting organic light-emitting diodes (OLEDs) is reported. Through solution processing from fluorinated solvents, a nano-particlescattering layer (NPSL) can be deposited directly on top of small molecule OLEDs without affecting their electrical performance. The scattering length for light inside the NPSL is determined from transmission measurements and found to be in agreement with Mie scattering theory. Furthermore, the dependence of the light outcoupling enhancement on electron transport layer thickness is studied. Depending on the electron transport layer thickness, the NPSL enhances the external quantum efficiency of the investigated white OLEDs by between 1.5 and 2.3-fold. For a device structure that has been optimized prior to application of the NPSL, the maximum external quantum efficiency is improved from 4.7% to 7.4% (1.6-fold improvement). In addition, the scattering layer strongly reduces the undesired shift in emission color with viewing angle.
Original languageEnglish
Article number233301
Number of pages5
JournalApplied Physics Letters
Volume107
DOIs
Publication statusPublished - 7 Dec 2015

Keywords

  • Organic light emitting diodes
  • Solvent
  • Nanoparticles
  • Visible spectra
  • Light scattering

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