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Improving the Brightness and Daylight Contrast of Organic Light‐Emitting Diodes
Author(s) -
Vaenkatesan V.,
Wegh R. T.,
Teunissen J.P.,
Lub J.,
Bastiaansen C. W. M.,
Broer D. J.
Publication year - 2005
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200400122
Subject(s) - polarizer , daylight , materials science , optics , brightness , contrast ratio , optoelectronics , light emitting diode , contrast (vision) , oled , sunlight , diode , total internal reflection , liquid crystal , ray , physics , nanotechnology , layer (electronics) , birefringence
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.