We thank the Commission of the European Community (Project POWERPLAY; No. GRD1-2000-25820) for supporting this collaboration.
Improving the Brightness and Daylight Contrast of Organic Light-Emitting Diodes†
Article first published online: 13 JAN 2005
Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Advanced Functional Materials
Volume 15, Issue 1, pages 138–142, January, 2005
How to Cite
Vaenkatesan, V., Wegh, R. T., Teunissen, J.-P., Lub, J., Bastiaansen, C. W. M. and Broer, D. J. (2005), Improving the Brightness and Daylight Contrast of Organic Light-Emitting Diodes. Adv. Funct. Mater., 15: 138–142. doi: 10.1002/adfm.200400122
- Issue published online: 13 JAN 2005
- Article first published online: 13 JAN 2005
- Manuscript Accepted: 22 JUL 2004
- Manuscript Received: 9 MAR 2004
- Light-emitting diodes, organic;
- Liquid crystals;
- Thin films
For most applications of displays based on organic light-emitting diodes (LEDs), it is desirable to have good daylight contrast in combination with a high intensity of emitted light. The conventional approaches to enhance the daylight contrast, using a black cathode or circular polarizers, result in a significant loss of light emitted by the LED. A rather novel approach to enhance daylight contrast while keeping loss of emitted light to a minimum is the introduction of a chiral-nematic film in the device. This approach leads to an increase in light efficiency by a factor of 1.8 (with respect to circular polarizers) with some loss in daylight contrast values within the reflection band of the chiral-nematic film. Outside the reflection band, however, the contrast approaches infinity.