Browsing by Author "Chen, Yung-Shiuan"

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Enhanced power efficiency of single-layer white triplet polymer light-emitting diodes by blending with polymer oxides
(2008)
Chen, Yung-Shiuan
;
Chien, Shang-Chieh
;
Chen, Fang-Chung
;
Lian, Jan-Tian
;
Tsou, Chien-Lung
In this study, we have demonstrated enhanced performance of blue, red and white phosphorescent polymer light-emitting diodes (PLEDs) by blending poly(ethylene glycol) (PEG) into the active layer of the devices. By introducing PEG into the PLEDs, the turn-on voltages of these devices became lower than those of the conventional devices. In addition, the luminance efficiency and the external quantum efficiency of the blue and while phosphorescent PLEDs were both improved. Most important of all, because of the lower operating voltage, the higher power efficiency (7.3 lm/W, 1.5 lm/W, 4.61m1W) of the blue, red and white phosphorescent PLEDs than those of the control devices (2.9 lm/W, 1. 1 lm/W, 1. 9 lM/W) have been achieved, respectively. Finally, the improvement mechanism will be discussed.
Single-layer triplet white polymer light-emitting diodes incorporating polymer oxides: Effect of charge trapping at phosphorescent dopants
(2009-01-26)
Chen, Fang-Chung
;
Chien, Shang-Chieh
;
Chen, Yung-Shiuan
;
光電工程學系
;
顯示科技研究所
This paper describes the effects of charge trapping on the device performances of triplet polymer light-emitting diodes (PLEDs) after the cathode contact had been improved through the blending of poly(ethylene glycol) (PEG) into the active layer. The external quantum efficiency (EQE) was enhanced when the dopant tended to trap electrons. In contrast, we observed no EQE enhancement for the device featuring a hole-trapping dopant. Because PEG promoted electron injection, more electrons were trapped in the triplet molecules, thereby enhancing the probability of recombination. Finally, after incorporating PEG, we further achieved white PLEDs exhibiting both high EQE and high power efficiency.