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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/47391

Title: Comparison of light out-coupling enhancements in single-layer bluephosphorescent organic light emitting diodes using small-molecule or polymer hosts
Authors: Chih-I Wu
Yung-Ting Chang
Shun-Wei Liu
Chih-Hsien Yuan
Yu-Hsuan Ho
Kuan-Yu Chen
Yi-Ting Lee
Min-Fei Wu
Chih-Chien Lee
Pei-Kuen Wei
Chin-Ti Chen
Contributors: 國立臺灣海洋大學:光電科學研究所
Date: 2013-11
Issue Date: 2018-07-18T01:50:04Z
Publisher: Journal of Applied Physics
Abstract: Abstract: Single-layer blue phosphorescence organic light emitting diodes (OLEDs) with either small-molecule or polymer hosts are fabricated using solution process and the performances of devices with different hosts are investigated. The small-molecule device exhibits luminous efficiency of 14.7 cd/A and maximum power efficiency of 8.39 lm/W, which is the highest among blue phosphorescence OLEDs with single-layer solution process and small molecular hosts. Using the same solution process for all devices, comparison of light out-coupling enhancement, with brightness enhancement film (BEF), between small-molecule and polymer based OLEDs is realized. Due to different dipole orientation and anisotropic refractive index, polymer-based OLEDs would trap less light than small molecule-based OLEDs internally, about 37% better based simulation results. In spite of better electrical and spectroscopic characteristics, including ambipolar characteristics, higher carrier mobility, higher photoluminescence quantum yield, and larger triplet state energy, the overall light out-coupling efficiency of small molecule-based devices is worse than that of polymer-based devices without BEF. However, with BEF for light out-coupling enhancement, the improved ratio in luminous flux and luminous efficiency for small molecule based device is 1.64 and 1.57, respectively, which are significantly better than those of PVK (poly-9-vinylcarbazole) devices. In addition to the theoretical optical simulation, the experimental data also confirm the origins of differential light-outcoupling enhancement. The maximum luminous efficiency and power efficiency are enhanced from 14.7 cd/A and 8.39 lm/W to 23 cd/A and 13.2 lm/W, respectively, with laminated BEF, which are both the highest so far for single-layer solution-process blue phosphorescence OLEDs with small molecule hosts.
Relation: 114(17)
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/47391
Appears in Collections:[光電科學研究所] 期刊論文

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