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Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis
Wang, Qi; Ding, Junqiao; Ma, Dongge; Cheng, Yanxiang; Wang, Lixiang; Jing, Xiabin; Wang, Fosong
2009-01-09
Source PublicationADVANCED FUNCTIONAL MATERIALS
ISSN1616-301X
Volume19Issue:1Pages:84-95
AbstractBy incorporating two phosphorescent dyes, namely, iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C(2)']picolinate (Flrpic) for blue emission and bis(2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1 H-benzoimidazol-N,C(3)) iridium(acetylacetonate) ((fbi)(2)Ir(acac)) for orange emission, into a single-energy well-like emissive layer, an extremely high-efficiency white organic light-emitting diode (WOLED) with excellent color stability is demonstrated. This device can achieve a peak forward-viewing power efficiency of 42.5 lm W(-1), corresponding to an external quantum efficiency (EQE) of 19.3% and a current efficiency of 52.8 cd A(-1). Systematic studies of the dopants, host and dopant-doped host films in terms of photophysical properties (including absorption, photoluminescence, and excitation spectra), transient photoluminescence, current density-voltage characteristics, and temperature-dependent electroluminescence spectra are subsequently performed, from which it is concluded that the emission natures of Flrpic and (fbi)(2)Ir(acac) are, respectively, host-guest energy transfer and a direct exciton formation process. These two parallel pathways serve to channel the overall excitons to both dopants, greatly reducing unfavorable energy losses. It is noteworthy that the introduction of the multifunctional orange dopant (fbi)(2)Ir(acac) (serving as either hole-trapping site or electron-transporting channel) is essential to this concept as it can make an improved charge balance and broaden the recombination zone. Based on this unique working model, detailed studies of the slight color-shift in this WOLED are performed. It is quantitatively proven that the competition between hole trapping on orange-dopant sites and undisturbed hole transport across the emissive layer is the actual reason. Furthermore, a calculation of the fraction of trapped holes on (fbi)(2)Ir(acac) sites with voltage shows that the hole-trapping effect of the orange dopant is decreased with increasing drive voltage, leading to a reduction of orange emission.
DOI10.1002/adfm.200800918
Indexed BySCI
Language英语
WOS IDWOS:000262584800007
PublisherWILEY-V C H VERLAG GMBH
Citation statistics
Cited Times:325[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.iccas.ac.cn/handle/121111/68302
Collection中国科学院化学研究所
Corresponding AuthorWang, Qi
AffiliationChinese Acad Sci, Grad Sch, Changchun Inst Appl Chem, State Key Lab Polymer Phys & Chem, Changchun 130022, Peoples R China
Recommended Citation
GB/T 7714
Wang, Qi,Ding, Junqiao,Ma, Dongge,et al. Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis[J]. ADVANCED FUNCTIONAL MATERIALS,2009,19(1):84-95.
APA Wang, Qi.,Ding, Junqiao.,Ma, Dongge.,Cheng, Yanxiang.,Wang, Lixiang.,...&Wang, Fosong.(2009).Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis.ADVANCED FUNCTIONAL MATERIALS,19(1),84-95.
MLA Wang, Qi,et al."Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis".ADVANCED FUNCTIONAL MATERIALS 19.1(2009):84-95.
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