• Title/Summary/Keyword: Organic light-emitting diodes (OLEDs)

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Cathode interface engineering for stable and efficient organic light-emitting diodes

  • Qiu, Yong;Duan, Lian;Li, Yang
    • 한국정보디스플레이학회:학술대회논문집
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    • 2007.08b
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    • pp.1199-1202
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    • 2007
  • The improvement of the electron injection is of critical importance for obtaining efficient and stable organic light-emitting diodes(OLEDs). Here, we report some of our recent results on the development of new cathode interlayer materials for OLEDs. Some of our new materials show performance superior to that of LiF.

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Fully Solution-Processed Green Organic Light-Emitting Diodes Using the Optimized Electron Transport Layers (최적화된 전자 수송층을 활용한 완전한 용액공정 기반 녹색 유기발광다이오드)

  • Han, Joo Won;Kim, Yong Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.7
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    • pp.486-489
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    • 2018
  • Solution-processed organic light-emitting diodes (OLEDs) have the advantages of low cost, fast fabrication, and large-area devices. However, most studies on solution-processed OLEDs have mainly focused on solution-processable hole transporting materials or emissive materials. Here, we report fully solution-processed green OLEDs including hole/electron transport layers and emissive layers. The electrical and optical properties of OLEDs based on solution-processed TPBi (2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) as the electron transport layer were investigated with respect to the spin speed and the number of layers. The performance of OLEDs with solution-processed TPBi exhibits a power efficiency of 9.4 lm/W. We believe that the solution-processed electron transport layers can contribute to the development of efficient fully solution-processed multilayered OLEDs.

Electrical Characteristics of Organic Light Emitting Diodes (OLED) using the cathode change (다양한 혼합 전극을 사용한 Organic Light Emitting Diodes(OLEDs)의 전기적 특성)

  • Lee, Hyun-Koo;Kim, Jun-Ho;Kim, Young-Kwan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.475-476
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    • 2005
  • Efficient electron injection is essential to achieve bright and efficient organic light-emitting diodes (OLEDs). In spite of high work function of Al, it is a common cathode because of its stability. In this paper, to overcome the poor electron injection in OLEDs with Al cathode, OLEDs with various composite cathodes were fabricated and investigated using a conventional OLEDs structure of indium tin oxide ITO/NPB(40 nm)/$Alq_3$(50 nm)/Al. composite cathodes were composed of alkaline materials such as Ca and Li, Al deposition or codeposited with AI. We showed best performance at the device with composite cathode (LiF/Al).

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Characteristics and fabrications of high brightness organic light emitting diode(OLED) (고휘도 유기발광소자 제작 및 특성)

  • Jang, Yoon-Kee;Lee, Jun-Ho;Nam, Hyo-Duk;Park, Chin-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.316-319
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    • 2001
  • Organic light emitting diodes(OLEDs) with a hole injection layer inserted between Indium-Tin-Oxide(ITO) anode and hole transport layer were fabricated. The effect of plasma treatment on the surface properties of Indium-Tin-Oxide(ITO) anode were studied. The electrical and optical characteristics of the fabricated organic light emitting diodes(OLEDs) were also studied. The diode including of plasma treated ITO substrate and the hole injection layer, which showed the luminance of 5280 $cd/m^{2}$ at 8 V

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Characteristics and fabrications of high brightness organic light emitting diode(OLED) (고휘도 유기발광소자 제작 및 특성)

  • 장윤기;이준호;남효덕;박진호
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11a
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    • pp.316-319
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    • 2001
  • Organic light emitting diodes(OLEDs) with a hole injection layer inserted between Indium-Tin-Oxide(ITO) anode and hole transport layer were fabricated. The effect of plasma treatment on the surface properties of Indium-Tin-Oxide(ITO) anode were studied. The electrical and optical characteristics of the fabricated organic light emitting diodes(OLEDs) were also studied. The diode including of plasma treated ITO substrate and the hole injection layer, which showed the luminance of 5280 cd/㎡ at 8 V

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Improved Electron Injection on Organic Light-emitting Diodes with an Organic Electron Injection Layer

  • Kim, Jun-Ho;Suh, Chung-Ha;Kwak, Mi-Young;Kim, Bong-Ok;Kim, Young-Kwan
    • Transactions on Electrical and Electronic Materials
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    • v.6 no.5
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    • pp.221-224
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    • 2005
  • To overcome of poor electron injection in organic light-emitting diodes (OLEDs) with Al cathode, a thin layer of inorganic insulating materials, like as LiF, is inserted between an Al cathode and an organic electron transport layer. Though the device, mentioned above, improves both turn on voltage and luminescent properties, it has some problems like as thickness restriction, less than 2 nm, and difficulty of deposition control. On the other hand, Li organic complex, Liq, is less thickness restrictive and easy to deposit and it also enhances the performance of devices. This paper reports the improved electron injection on OLEDs with another I A group metal complex, Potassium quinolate (Kq), as an electron injection material. OLEDs with organic complexes showed improved turn-on voltage and luminous efficiency which are remarkably improved compared to OLEDs with Al cathode. Especially, OLEDs with Kq have longer life time than OLEDs with Liq.

Recent Research Highlights in Blue Fluorescent Emitters in Organic Light-Emitting Diodes (유기발광 다이오드(OLED) 및 이를 위한 청색형광체)

  • Park, Young Il;Kim, Jin Chul;Seo, Bongkuk;Cho, Deug-Hee
    • Applied Chemistry for Engineering
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    • v.25 no.3
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    • pp.233-236
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    • 2014
  • Organic light emitting diodes (OLEDs) received much attention from both academia and industry as the next-generation flat panel displays. However, to produce high quality OLEDs, there are still many challenges to overcome. Especially, in full color OLEDs, the intrinsic wide band gap of the blue emitting materials results in inferior efficiency compared to those of green and red emitting materials. Therefore, extensive research efforts have been devoted to develop efficient blue emitting materials. This review briefly summarizes the basics of OLEDs and introduces highlights of research efforts in blue-emitting materials.

Electrical and Optical Study of PLED & OLEDS Structures

  • Mohammed, BOUANATI Sidi;SARI, N. E. CHABANE;Selma, MOSTEFA KARA
    • Transactions on Electrical and Electronic Materials
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    • v.16 no.3
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    • pp.124-129
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    • 2015
  • Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq3). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

View Angle Emission Pattern in ITO-TPD-$Alq_3$-LiF-Al Organic Light-Emitting Diodes

  • Kim, Tae-Wan;Park, Clara
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.193-194
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    • 2009
  • This report makes an important correction to estimating angular dependent emission pattern of Organic Light-Emitting Diodes (OLEDs). Today, experiments on measuring angular light intensity of OLEDs are conducted without considering the difference between the view angle identified by photodiode and the actual angle being measured. ITO-TPD-$Alq_3$-LiF-Al Organic Light-Emitting Diode was used to find out the degree of the error. In this case, the difference in average was about $1^*$, which is highly significant. Since the difference varies from case to case, the need for adjustment must be evaluated for each case.

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Influence of Electrode and Thickness of Organic Layer to the Emission Spectra in Microcavity Organic Light Emitting Diodes (마이크로캐비티 OLED의 전극과 유기물층 두께가 발광 스펙트럼에 미치는 영향)

  • Kim, Chang-Kyo;Han, Ga-Ram;Kim, Il-Yeong;Hong, Chin-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.11
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    • pp.1183-1189
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    • 2012
  • Organic light-emitting diodes (OLEDs) using microcavity effect have attracted great attention because they can reduce the width of emission spectra from organic materials, and enhance brightness from the same material. We demonstrate the simulation results of the radiation properties from top-emitting organic light-emitting diodes (TE-OLEDs) with microcavity structures based on the general electromagnetic theory. Organic materials such as N,N'-di (naphthalene-1-yl)-N,N'-diphenylbenzidine (NPB) as a hole transport layer and tris (8-hydroxyquinoline) ($Alq_3$) as emitting and electron transporting layer are used to form the OLEDs. The organic materials were sandwiched between anode such as Ni or Au and cathode such as Al, Ag, or Al:Ag. The devices were characterized with electroluminescence phenomenon. We confirmed that the simulation results are consistent with experimental results.