Very high-efficiency and low voltage phosphorescent organic light-emitting diodes based on a <i>p-i-n</i> junction

He, Gufeng; Schneider, O.; Qin, Dashan; Zhou, Xiang; Pfeiffer, Martin; Leo, Karl

doi:10.1063/1.1702143

Cited by 170 publications

(115 citation statements)

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“…This approach enables internal quantum efficiencies reaching unity [1] and operational lifetimes suitable for commercial display applications. [2,3,4,5,6] A common technique to fabricate multicolor pixelated OLED devices is shadow mask patterning. However, there are severe limitations…”

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confidence: 99%

Photo‐patterning of Highly Efficient State‐of‐the‐Art Phosphorescent OLEDs Using Orthogonal Hydrofluoroethers

Krotkus

Ventsch

Kasemann

et al. 2014

Advanced Optical Materials

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Together with "back plane" electronic components and highly efficient "front plane" light-emitting devices, the successful implementation of pixel patterning is a key requirement for the success of organic light-emitting diode (OLED) displays. Prerequisites for patterning techniques include cost-efficiency, scalability to large area substrates (≥Gen 8), registration between multiple layers, and compatibility with state-of-the-art OLED technology. At present, state-of-the-art OLEDs are predominantly based on multilayered thin films of thermally evaporated small molecules and frequently contain phosphorescent emitters. This approach enables internal quantum efficiencies reaching unity [1] and operational lifetimes suitable for commercial display applications. [2,3,4,5,6] A common technique to fabricate multicolor pixelated OLED devices is shadow mask patterning. However, there are severe limitations

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confidence: 99%

Photo‐patterning of Highly Efficient State‐of‐the‐Art Phosphorescent OLEDs Using Orthogonal Hydrofluoroethers

Krotkus

Ventsch

Kasemann

et al. 2014

Advanced Optical Materials

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“…High-efficiency OLEDs have also been reported in various HIL/HTL configurations. [4][5][6][7][8] Furthermore, low-voltage and high-efficiency OLEDs can be realized with a p-doped HIL [9][10][11] in which the layer thickness can be readily adjusted for optimal light extraction. It has been suggested that the enhanced performance in HIL/HTL devices is due to a sequence of cascaded hole-injection barriers present in the HIL/HTL/ETL structure, which produces a "balanced" electron-hole recombination at the HTL/ETL interface.…”

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confidence: 99%

Current efficiency in organic light-emitting diodes with a hole-injection layer

Wang

Klubek

Tang

2008

Applied Physics Letters

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We have systematically investigated the effect of layer structures on the current efficiency of prototypical hole-injection layer ͑HIL͒/hole-transport layer ͑HTL͒/electron-transport layer ͑ETL͒ organic light-emitting diodes based on 4 , 4Ј ,4Љ-tris͓N-͑3-methylphenyl͒-N-phenylamino͔-triphenylamine ͑MTDATA͒ as the HIL, 4 , 4Ј-bis͓N-͑1-naphthyl͒-N-phenylamino͔biphenyl ͑NPB͒ as the HTL, and tris͑8-quinolinolato͒aluminum ͑Alq͒ as the ETL. With bilayer devices, the current efficiency is limited by exciplex emissions in the case of MTDATA/Alq and quenching of Alq emissions by NPB + radical cations in NPB/Alq. The improved current efficiency in trilayer MTDATA/NPB/Alq devices can be attributed to a reduction in NPB + radical cations at the NPB/Alq interface and a strong electric field in the NPB layer. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2978349͔Since they first appeared in the 1980s, 1 organic lightemitting diodes ͑OLEDs͒ have received much attention due to their potential use as a full-color display technology. Although the efficiency and the operational life of OLEDs have vastly improved through intensive research effort, the mechanism underlying these key performance parameters are not well understood. The basic OLED device has a bilayer organic thin-film structure such as indium tin oxide ͑ITO͒/4,4Ј-bis͓N-͑1-naphthyl͒-N-phenylamino͔biphenyl ͑NPB͒/Alq/LiF/Al, where ITO is the anode and LiF/Al is the cathode, and NPB and Alq are the hole-transport layer ͑HTL͒ and the electron-transport layer ͑ETL͒, respectively. During operation, the injected holes and electrons recombine at or near the HTL/ETL interface, producing electroluminescence ͑EL͒. It has been shown that much improved OLED performance can be realized using a HIL/HTL structure, where HIL is the "hole-injection" layer inserted between the anode and the HTL. For example, with CuPc 2 as the HIL as in CuPc/NPB/Alq where Alq also functions as the emissive layer, long-lived OLEDs have been obtained. Another common HIL material is 4 , 4Ј ,4Љ-tris͓N-͑3-methylphenyl͒-N-phenylamino͔triphenylamine ͑MTDATA͒, 3 with which enhanced current efficiency and operational stability have been demonstrated. High-efficiency OLEDs have also been reported in various HIL/HTL configurations. 4-8 Furthermore, low-voltage and high-efficiency OLEDs can be realized with a p-doped HIL 9-11 in which the layer thickness can be readily adjusted for optimal light extraction. It has been suggested that the enhanced performance in HIL/HTL devices is due to a sequence of cascaded hole-injection barriers present in the HIL/HTL/ETL structure, which produces a "balanced" electron-hole recombination at the HTL/ETL interface. 12,13 In this paper, we systematically investigate the effect of the HIL on OLED performance characteristics, specifically the cause for current efficiency enhancement. Figure 1 shows the multilayer OLED structure and the molecular structures for the HIL ͑MTDATA͒, HTL ͑NPB͒, and ETL ͑Alq͒. The Fabrication of OLEDs by physical vapor deposition is described elsewhe...

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“…The grounds for achieving very similar electrical properties of the OLED samples is to use doped ETL and HTL layers and a p-i-n OLED structure. 15,16 Having this in mind, one can determine g cb as a constant fitting parameter by comparing measured EQE values (without a half-ball lens) and simulated EQE air values using Eq. (16).…”

Section: Verification Of the Model And Discussionmentioning

confidence: 99%

“…15,16 Having this in mind, one can determine g cb as a constant fitting parameter by comparing measured EQE values (without a half-ball lens) and simulated EQE air values using Eq. (16). The values for the measured EQE are taken at a low current density before the efficiency roll-off sets in (Fig.…”

Section: Verification Of the Model And Discussionmentioning

confidence: 99%

“…The OLED architecture contains doped charge transport layers and intrinsic charge blocking layers. 15,16 We employ 4wt% of NDP-2 (Novaled AG) doped in the NHT-5 (Novaled AG) as hole injection and transport layer (HTL). As electron and hole blocking layers (EBL/HBL), we All devices are fabricated by thermal evaporation on ITO prestructured glass substrates in an UHV chamber (Kurt J. Lesker) with a base pressure below 10 À7 mbar.…”

Section: Device Fabrication and Measurementsmentioning

confidence: 99%

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Integrated optical model for organic light-emitting devices

Mladenovski

Hofmann

Reineke

et al. 2011

Journal of Applied Physics

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One of the most important parameters of organic light-emitting devices (OLEDs) in their application for illumination or displays is their efficiency. In order to maximize the efficiency, one needs to understand all loss mechanisms and effects present in these devices and properly model them. For that purpose, we introduce an integrated model for light emission from OLEDs. The model takes into account the exciton decay time change and light outcoupling. Furthermore, it shows how to calculate the external quantum efficiency, the spectral radiance and the luminous current efficacy of OLEDs. The overall theory is experimentally verified through a range of measurements done on a set of green OLED samples with an Ir-based phosphorescent emitter. From the analysis of simulations and experiments one can estimate the charge balance in the OLED stack and the radiative efficiency of the emitter.

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Very high-efficiency and low voltage phosphorescent organic light-emitting diodes based on a p-i-n junction

Cited by 170 publications

References 22 publications

Photo‐patterning of Highly Efficient State‐of‐the‐Art Phosphorescent OLEDs Using Orthogonal Hydrofluoroethers

Photo‐patterning of Highly Efficient State‐of‐the‐Art Phosphorescent OLEDs Using Orthogonal Hydrofluoroethers

Current efficiency in organic light-emitting diodes with a hole-injection layer

Integrated optical model for organic light-emitting devices

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