Research Highlights

• Subject Categories:
  • Physics
  • Materials
  • Chemistry

Published online: 6 May 2009 | doi:10.1038/nchina.2009.93

Electronics: Tandem light

Felix Cheung

Introduction

© (2009) Dongge Ma

The white organic light-emitting diode, or WOLED, has been touted as the next wonder technology for lighting applications, ranging from general-purpose illumination to flat-panel displays. WOLED devices are superior to current OLED devices because they are brighter, thinner and more flexible. Dongge Ma and co-workers at the Chinese Academy of Sciences in Changchun¹ have now fabricated a high-performance WOLED device with a relatively simple architecture.

Ideally, a high-performance WOLED device should possess high power efficiency (high brightness versus low power) and stable spectral performance over its lifetime. One way to achieve this is by connecting a series of white-light emitting layers (EMLs) with charge generation layers (CGLs) because the brightness adds up in tandem.

The researchers largely improved the performance of their WOLED device by doing two things: first, they used an organic material with near 100% internal quantum efficiency to make two white-light EMLs; and secondly, they used a lithium-doped organic material to make an effective CGL.

By optimizing the thickness of each organic layer and the doping concentration of lithium, the fabricated device can emit stable white light with forward-viewing power efficiency up to 45.2 lumens per watt. More importantly, the brightness of the device was 2.3 times that of the original EML.

The findings show that the combination of effective CGLs and efficient EMLs is essential to realizing high-performance tandem WOLEDs.

The authors of this work are from:
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China.

Reference

1. Wang, Q. et al. A high-performance tandem white organic light-emitting diode combining highly effective white-units and their interconnection layer. J. Appl. Phys. 105, 076101 (2009).
    | Article | ChemPort |