P-185: Low-Drive-Voltage OLEDs with a Buffer Layer Having Molybdenum Oxide

Ikeda, Hisao; Sakata, Junichiro; Hayakawa, Masahiko; Aoyama, Teruyoshi; Kawakami, Toru; Kamata, Koichiro; Iwaki, Yuji; Seo, Satoshi; Noda, Yumiko; Nomura, Ryoji; Yamazaki, Shunpei

doi:10.1889/1.2433672

Cited by 70 publications

(42 citation statements)

References 3 publications

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“…Various kinds of p-type dopants have been developed, including organic dopant such as tetrafluoro-tetracyano-quinodimethane ͑F 4 -TCNQ͒, 6 metal halides such as antimony pentachloride ͑SbCl 5 ͒, 7 ferric chloride ͑FeCl 3 ͒ ͑Ref. 8͒ and copper iodide ͑CuI͒, 9 and metal oxides such as vanadium oxide ͑V 2 O 5 ͒, 10 tungsten oxide ͑WO 3 ͒, 11 molybdenum oxides ͑MoO x ͒, 12,13 and rhenium oxide ͑ReO 3 ͒. 14 Many groups presented that the p-dopants form charge transfer ͑CT͒ complexes with hole transporting organic materials by electron transfer from organic molecules to the dopant.…”

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confidence: 99%

Effectiveness of p-dopants in an organic hole transporting material

Lee

Leem

Kim

et al. 2009

Applied Physics Letters

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We investigated the effectiveness of p-dopants to generate holes in a hole transporting material by comparing the absorption in visible-near-infrared and infrared regions and current density-voltage characteristics. CuI, MoO3, and ReO3 having different work functions were doped in a hole transporting organic material, 4,4′,4″-tris(N-(2-naphthyl)-N-phenylamino)-triphenylamine (2TNATA). Formation of charge transfer (CT) complexes increases linearly with increasing doping concentration for all the dopants. Dopants with higher work function (ReO3>MoO3>CuI) are more effective in the formation of CT complexes and in the generation of the charges in the doped films.

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confidence: 99%

Effectiveness of p-dopants in an organic hole transporting material

Lee

Leem

Kim

et al. 2009

Applied Physics Letters

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“…Various p-dopants for a hole transporting layer ͑HTL͒ have been developed, which include an organic-based dopant of F 4 -TCNQ, [5][6][7][8] metal halides such as FeCl 3 and SbCl 5 , 9,10 and metal oxides like WO 3 and MoO 3 . 11,12 Recently, our group has also developed another metal-oxide p-doping system based on rhenium oxide ͑ReO 3 ͒, showing an efficient p-doping property coming from the formation of charge-transfer complex within the HTL. 13 Furthermore, the developed p-doping system facilitates easy codeposition with organic molecules by a conventional thermal evaporator due to low-temperature deposition ͑ϳ350°C͒ of ReO 3 .…”

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confidence: 99%

Rubidium-Carbonate-Doped 4,7-Diphenyl-1,10-phenanthroline Electron Transporting Layer for High-Efficiency p-i-n Organic Light Emitting Diodes

Leem

Kim

et al. 2009

Electrochem. Solid-State Lett.

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We investigated the electrical properties and charge transport mechanisms of a rubidium-carbonate ͑Rb 2 CO 3 ͒-doped 4,7-diphenyl-1,10-phenanthroline ͑Bphen͒ electron transporting layer ͑ETL͒. The electron-only devices and photoemission spectroscopy analysis revealed that the formation of doping-induced gap states dominantly contributes to the improvement of carrier transport characteristics of the doped system. High-efficiency green phosphorescent p-doping/intrinsic/n-doping ͑p-i-n͒ organic light emitting diodes were demonstrated using the Rb 2 CO 3 -doped Bphen ETL and rhenium oxide ͑ReO 3 ͒-doped N, ,4Ј-diamine hole transporting layer, exhibiting an external quantum efficiency of 19.2%, power efficiency of 76 lm/W, and low operation voltage of 3.6 V at 1000 cd/m 2 . © 2008 The Electrochemical Society. ͓DOI: 10.1149/1.3007239͔ All rights reserved.Manuscript submitted August 26, 2008; revised manuscript received October 6, 2008. Published October 27, 2008 Organic light emitting diodes ͑OLEDs͒ have been recognized and partially realized as next-generation flat-panel displays and solid-state lighting.1,2 Highly efficient OLEDs with external quantum efficiency ͑EQE͒ over 20% have been demonstrated through the development of materials and device structures.2-4 However, a relatively high driving voltage causes loss of power efficiency. To overcome the limitations, a doping concept has been applied to the conventional OLED structure and created promising p-doping/intrinsic/ n-doping ͑p-i-n͒ OLEDs exhibiting low operation voltage, high efficiency, and long lifetime. 5-8The doping technology of charge-transporting layers is a key issue in fabricating high-performance p-i-n OLEDs with low power consumption. Various p-dopants for a hole transporting layer ͑HTL͒ have been developed, which include an organic-based dopant of F 4 -TCNQ, 5-8 metal halides such as FeCl 3 and SbCl 5 , 9,10 and metal oxides like WO 3 and MoO 3 .11,12 Recently, our group has also developed another metal-oxide p-doping system based on rhenium oxide ͑ReO 3 ͒, showing an efficient p-doping property coming from the formation of charge-transfer complex within the HTL. 13 Furthermore, the developed p-doping system facilitates easy codeposition with organic molecules by a conventional thermal evaporator due to low-temperature deposition ͑ϳ350°C͒ of ReO 3 . In contrast, there are fewer material systems reported to date for n-doping of an electron transporting layer ͑ETL͒. Alkali metals such as Li and Cs 5-7 or alkali metal carbonate like Cs 2 CO 3 14,15 have been applied as n-dopants. However, limited work [14][15][16] has been carried out for the application of a metal carbonate-based n-doping system, requiring further research and development on the efficient n-doping system.In this work, we report on the electrical properties and possible charge-transport mechanisms of a newly developed rubidium carbonate ͑Rb 2 CO 3 ͒-doped ETL system by means of a single carrier device test and photoemission spectroscopy analysis. Highefficiency p-i-n OLEDs are also ...

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“…The most popular way to facilitate charge injection at the organic interface was to use p-doped or n-doped charge transport layers [1][2][3][4][5][6][7][8]. The p-or n-doped charge transport layers were effective in improving the bulk mobility of charge transport material and inducing a high current density because of little energy barrier for charge injection.…”

Section: Introductionmentioning

confidence: 99%