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Proceedings Paper

Harvest of triplet excitons in fluorescence emission layer based on a wide band gap host of TcTa for efficient white organic light emitting diodes
Author(s): Jeong-Ik Lee; Hye Yong Chu; Yong Suk Yang; Lee-Mi Do; Sung Mook Chung; Sang-Hee Ko Park; Chi-Sun Hwang
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Paper Abstract

Selective energy transfer from triplet states of the fluorescent blue emission layer to a red phosphorescent dye in a neighbored triplet harvesting layer has been achieved, which has provided improved efficiency with emissions from fluorescent and phosphorescent dyes. First of all, it is crucial to find a wide band gap host for a fluorescent blue emission layer which has larger triplet state band gap than green or red phosphorescent dye. It was found that TcTa is a good wide band gap host for fluorescent blue dopant(BD) and a efficient blue device was obtained. A phosphorescent red dopant (RD) was introduced into a neighboring electron transporting layer to harvest triplet states in the fluorescent blue emission layer and by optimizing the distance between the blue emission layer and the red triplet harvesting layer, we have succeeded in obtaining the balanced emission of the blue and the red emissions with high efficiency from the device structure of NPB/TcTa:BD/BAlq/BAlq:RD/BAlq/LiF/Al. The device showed maximum external quantum efficiency of 16 % at 0.1 mA/cm2 and 13 % of external quantum efficiency, (0.29, 0.23) of CIE coordinates and 920 cd/m2 at 10 mA/cm2. To realize RGB WOLED, a fluorescent green dopant was introduced into the blue emission layer. The RGB WOLED was successfully obtained through optimization of doping concentration for green dopant and it showed 10 % of external quantum efficiency, (0.36, 0.36) of CIE coordinates and 1400 cd/m2 at 10 mA/cm2.

Paper Details

Date Published: 16 October 2007
PDF: 4 pages
Proc. SPIE 6655, Organic Light Emitting Materials and Devices XI, 66550I (16 October 2007); doi: 10.1117/12.734417
Show Author Affiliations
Jeong-Ik Lee, Electronics and Telecommunications Research Institute (South Korea)
Hye Yong Chu, Electronics and Telecommunications Research Institute (South Korea)
Yong Suk Yang, Electronics and Telecommunications Research Institute (South Korea)
Lee-Mi Do, Electronics and Telecommunications Research Institute (South Korea)
Sung Mook Chung, Electronics and Telecommunications Research Institute (South Korea)
Sang-Hee Ko Park, Electronics and Telecommunications Research Institute (South Korea)
Chi-Sun Hwang, Electronics and Telecommunications Research Institute (South Korea)


Published in SPIE Proceedings Vol. 6655:
Organic Light Emitting Materials and Devices XI
Zakya H. Kafafi; Franky So, Editor(s)

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