High-brightness top-emissive polymer light-emitting diodes utilizing organic oxide/Al∕Ag composite cathode

Guo, Tzung‐Fang; Yang, Fuh-Shun; Tsai, Zen-Jay; Feng, Guan-Weng; Wen, Ten‐Chin; Hsieh, Sung-Nien; Chung, Chia-Tin; Wu, Chia-Jen

doi:10.1063/1.2234317

Cited by 17 publications

(8 citation statements)

References 23 publications

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“…Guo et al reported that high performance polymer and small molecule OLEDs with an organic oxide, poly(ethylene glycol) dimethyl ether (PEGDE). Because PEGDE can be evaporated at low temperature compared to other inorganic insulators and improves the device performance as much as the inorganic electron injection layers, it could be a good candidate for an organic electron injection layer [15][16][17]. In this study, the performance of PVK based PLEDs is improved by using PEO/Ca/Al cathode.…”

mentioning

confidence: 84%

Polymer light-emitting devices using poly(ethylene oxide) as an electron injecting layer

Rao

Huang

et al. 2010

Nano-Micro Lett

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The performance of polymer light emitting devices (PLEDs) based on polyvinyl carbazole (PVK) is improved by introducing a nanoscale interfacial thin layer, made of poly(ethylene oxide) (PEO), between the calcium cathode and the PVK emissive layer. It is believed that the PEO layer plays a key role in enhancing the device performance. In comparison to the device with Ca/Al as the cathode, the performance of the PLED with PEO/Ca/Al cathode, including the driving voltage, luminance efficiency is significantly improved. These improvements are attributed to the introduction of a thin layer of PEO that can lower the interfacial barrier and facilitate electron injection. Polymer light-emitting diodes (PLEDs) have attracted much interest worldwide since their discovery by Friend and co-workers in 1990 [1]. Engineering of the polymer-electrode interfacial properties is crucial to achieve balanced hole and electron injection for high efficiency operations. Low work function metals, such as calcium or barium are widely used as a cathode to facilitate electron injection [2][3][4][5][6][7][8]. These metals are very sensitive to moisture and oxygen and form detrimental quenching sites at areas near the interface between the electroluminescent (EL) layer and the cathode. In addition, metal ions formed at the metal/organic interface tend to migrate into the EL layer, thus, affecting the long term stability of devices [9]. To circumvent these problems, it is desirable to use high work-function metals (such as Al, Ag, or Au) as the cathode because of their better environmental stability and the simplicity of their device fabrication. To improve electron injection from high-work-function metals into the emitting layer, numerous approaches have been attempted [10,11]. For example, by inserting a thin layer of lithium fluoride, or cesium fluoride, between Al and the light emitting layer, the electron-injection ability could be significantly improved [10][11][12]. It was shown by the Cao et al. that the insertion of organic surfactant molecules between Al and the EL polymer could improve device performance up to the level obtained by low-work function metal cathode [11]. Li et al. reported that effective electron injection can be achieved by the insertion of an ultrathin aluminum oxide layer between the Al and the emitting layer [13]. Lee et al. reported that polystyrene sodium sulfonate inserted between MEH-PPV and Al significantly improves electron injection [14]. Guo et al. reported that high performance polymer and small molecule OLEDs with an organic oxide, poly(ethylene glycol) dimethyl ether (PEGDE). Because PEGDE can be evaporated at low temperature compared to other inorganic insulators and improves the device performance as much as the inorganic electron injection layers, it could be a good candidate for an organic electron injection layer [15][16][17]. In this study, the performance of PVK based PLEDs is improved by using PEO/Ca/Al cathode. When a thin PEO (5 nm) buffer layer is introduced between the PVK emissive layer an...

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mentioning

confidence: 84%

Polymer light-emitting devices using poly(ethylene oxide) as an electron injecting layer

Rao

Huang

et al. 2010

Nano-Micro Lett

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“…Then, the dividing amplitude is used to calculate the forward emission. The intensity of the forward emission ( , ) from the micro-cavity has been calculated via Equations (1)-(4) [27][28][29][30]: In order to analyze the effect of this micro-cavity in BOLEDs, we implemented a theoretical simulation of its mechanism and found that the transmission of the anode plays an important role in the forward emission. Here, micro-cavity OLEDs can be simplified as a Fabry-Pérot resonator.…”

Section: Optical Properties Of the Micro-cavity In Oledsmentioning

confidence: 99%

“…Then, the dividing amplitude is used to calculate the forward emission. The intensity of the forward emission ( , ) from the micro-cavity has been calculated via Equations (1)-(4) [27][28][29][30]: Assuming I 0 (λ, θ) as the emission of radiating dipoles in the emitting layer, after the wide-angle and multi-beam interferences inside the cavity, the light finally emits through the anode, which is semi-transparent. Then, the dividing amplitude is used to calculate the forward emission.…”

Section: Optical Properties Of the Micro-cavity In Oledsmentioning

confidence: 99%

Color-Tunable Organic Light Emitting Diodes for Deep Blue Emission by Regulating the Optical Micro-Cavity

et al. 2020

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Nowadays, most blue organic light emitting diodes (OLEDs) are fabricated by using sky-blue emitters which are more easily synthesized when compared with other deep blue emitters. Herein, we put forward a new idea of using an optical micro-cavity based on metal electrodes to regulate electroluminance (EL) spectra of sky-blue organic light emitting diodes to obtain a saturated deep blue emission with a narrowed full-width at half-maximum (FWHM). First, we simulate micro-cavity OLEDs and find that the transmission of the anode plays an important role in the forward emission. Meanwhile, the optical path of micro-cavity OLEDs as well as the phase shifting from electrodes influence the EL spectra and induce the extra intensity enhancement. The results show that when the resonant cavity optical path is regulated by changing the thickness of emitting layer (EML) from 25 nm to 75 nm in the micro-cavity, the EL peak of blue OLEDs has a redshift from 479 nm to 493 nm with FWHM shifting from 69.8 nm to 83.2 nm, when compared to the device without the micro-cavity, whose approximate EL peak and FWHM are 487 nm and 87 nm, respectively. However, the efficiency of electroluminescence decreases in micro-cavity OLEDs. We speculate that this is on account of the ohmic contact between ITO and Ag, the surface plasma effect and the rough morphology induced by Ag electrodes.

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“…The research was focalised on different topics such as: effect of doping of the organic semiconductor to increase the "transparency" of the energetic barrier to the injection of electron from the contact [6], influence of the trapped and interfacial charges generated in multilayer organic heterostructures on the properties of the device [7], charge tunnelling in multilayer stack and at the interface between organic and anode [8], influence of the thickness and doping of the emission layer on the properties of OLEDs [9], injection of the charge carriers from the electrodes and their migration in correlation with different types of cathodes [10][11][12][13], transport phenomena in organics [14; 15], stacked geometry for efficient double-sided emitting OLED [16], graded mixed layer as active layer to replace heterojunction in OLEDs [17]. The awarding in 2000 of the Nobel prize for researches in the field of conducting polymers has stimulated the development of OLEDs based on polymeric materials, application emphasised years before [18], opening the way of reducing the applied voltages (< 10 V) and increasing the brightness and lifetime.…”

Section: Introductionmentioning

confidence: 99%

Aromatic Derivatives Based Materials for Optoelectronic Applications

Stanculescu¹,

Stănculescu²

2013

Optoelectronics - Advanced Materials and Devices

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High-brightness top-emissive polymer light-emitting diodes utilizing organic oxide/Al∕Ag composite cathode

Cited by 17 publications

References 23 publications

Polymer light-emitting devices using poly(ethylene oxide) as an electron injecting layer

Polymer light-emitting devices using poly(ethylene oxide) as an electron injecting layer

Color-Tunable Organic Light Emitting Diodes for Deep Blue Emission by Regulating the Optical Micro-Cavity

Aromatic Derivatives Based Materials for Optoelectronic Applications

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