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Carrier Transport and Recombination Mechanism in Blue Phosphorescent Organic Light-Emitting Diode With Hosts Consisting of Cabazole- And Triazole-Moiety

Carrier Transport and Recombination Mechanism in Blue Phosphorescent Organic Light-Emitting Diode With Hosts Consisting of Cabazole- And Triazole-Moiety

Tian-You Cheng, Jiun-Haw Lee, Chia-Hsun Chen, Po-Hsun Chen, Po-Sheng Wang, Chuan-En Lin, Bo-Yen Lin, Yi-Hsin Lan, Yu-Hsuan Hsieh, Jau-Jiun Huang, Hsiu-Feng Lu, Ito Chao, Man-Kit Leung, Tien-Lung Chiu, Chi-Feng Lin

Sci Rep. 2019 Mar 6;9(1):3654.

PMID: 30842539

Abstract:

In this study, we demonstrated a blue phosphorescent organic light-emitting diode (BPOLED) based on a host with two carbazole and one trizole (2CbzTAZ) moiety, 9,9'-(2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)-1,3-phenylene)bis(9H-carbazole), that exhibits bipolar transport characteristics. Compared with the devices with a carbazole host (N,N'-dicarbazolyl-3,5-benzene, (mCP)), triazole host (3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, (TAZ)), or a physical mixture of mCP:TAZ, which exhibit hole, electron, and bipolar transport characteristics, respectively, the BPOLED with the bipolar 2CbzTAZ host exhibited the lowest driving voltage (6.55 V at 10 mA/cm2), the highest efficiencies (maximum current efficiency of 52.25 cd/A and external quantum efficiency of 23.89%), and the lowest efficiency roll-off, when doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) as blue phosphor. From analyses of light leakage of the emission spectra of electroluminescence, transient electroluminescence, and partially doped OLEDs, it was found that the recombination zone was well confined inside the emitting layer and the recombination rate was most efficient in a 2CbzTAZ-based OLED. For the other cases using mCP, TAZ, and mCP:TAZ as hosts, electrons and holes transported with different routes that resulted in carrier accumulation on different organic molecules and lowered the recombination rate.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP150405699	3-(Biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole		150405-69-9	Price
AP376367930	Bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III)		376367-93-0	Price

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