Enhanced Outcoupling in Organic Light-Emitting Diodes via a High-Index Contrast Scattering Layer

Tae Wook Koh, Joshua A. Spechler, Kyung Min Lee, Craig B. Arnold, Barry P. Rand

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

Despite high internal quantum efficiencies, planar organic light-emitting diodes (OLEDs) typically suffer from limited outcoupling efficiencies. To improve this outcoupling efficiency, we have developed a new thin (∼2 μm) light scattering layer that employs air voids (low-index scattering centers) embedded in a high-index polyimide matrix to effectively frustrate the substrate-trapped light, increasing the outcoupling efficiency. The porous polyimide scattering layers are created through the simple and scalable fabrication technique of phase inversion. The optical properties of the scattering layers have been characterized via microscopy, transmittance/haze measurements, and ellipsometry, which demonstrate the excellent scattering properties of these layers. We have integrated these films into a green OLED stack, where they show a 65% enhancement of the external quantum efficiency and a 77% enhancement of the power efficiency. Furthermore, we have integrated these layers into a white OLED and observed similar enhancements. Both the green and white OLEDs additionally demonstrate excellent color stability over wide viewing angles with the integration of this thin scattering layer.

Original languageEnglish (US)
Pages (from-to)1366-1372
Number of pages7
JournalACS Photonics
Volume2
Issue number9
DOIs
StatePublished - Aug 13 2015

All Science Journal Classification (ASJC) codes

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

Keywords

  • organic light-emitting diodes (OLEDs)
  • outcoupling efficiency
  • phase inversion
  • scattering layer

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