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**Chapter 4** 

© 2012 Jeong and Takezoe, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Jeong and Takezoe, licensee InTech. This is a paper distributed under the terms of the Creative Commons

**Effect of Photonic Structures in Organic** 

**Light-Emitting Diodes – Light Extraction** 

The development in organic light emitting diodes (OLEDs) has been one of the fastest growing research areas because of their potential applications in lighting and flat panel displays. Some commercialization of OLED devices such as lightings and displays has already been made. In particular, OLED displays are awaiting true commercialization toward large market. However, there are still several problems to be solved. Particularly two areas require ongoing improvements, 1) light extraction and 2) polarization. In this

As far as the material for organic light-emitting diodes (OLEDs) is concerned, semiconductor-based organic light emitters are the obvious choice because semiconducting organic light-emitting materials have reached a high level with internal quantum efficiencies of ~100% [1]. Unfortunately, however, most of this light is trapped inside OLEDs, and only 20% can be outcoupled because of the total internal reflection [2-7]. In this section, various light extraction technologies are reviewed to suppress guided light loss. In particular, the enhanced light extraction efficiency by means of photonic structures onto OLEDs is

OLEDs suffer from poor external efficiency that arises from Snell's law; i.e., light generated in a high-refractive-index layer tends to remain trapped in the layer due to total internal reflection [2,3]. In fact, whatever the internal quantum efficiency might be, the light

**and Polarization Characteristics** 

chapter the research activities in these two areas are summarized.

**2.1. Limited light extraction and improvement strategy** 

Soon Moon Jeong and Hideo Takezoe

http://dx.doi.org/10.5772/54669

**1. Introduction** 

**2. Light extraction** 

discussed in depth.

Additional information is available at the end of the chapter
