• Title/Summary/Keyword: organic emitting layer

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A Study on the Efficiency Effects of Capping Layer on the Top Emission Organic Light Emitting Diode (전면 유기발광 다이오드 기능층 캐핑레이어 적용에 따른 효율상승에 관한 연구)

  • Lee, DongWoon;Cho, Eou Sik;Jeon, Yongmin;Kwon, Sang Jik
    • Journal of the Semiconductor & Display Technology
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    • v.21 no.3
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    • pp.119-124
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    • 2022
  • Top emission organic light-emitting diode (TEOLED) is commonly used because of high efficiency and good color purity than bottom - emission organic light-emitting device (BEOLED). Unlike BEOLED, TEOLED contain semitransparent metal cathode and capping layer. Because there are many characteristics to consider just simple thickness change, optimizing organic thickness of TEOLED for microcavity is difficult. So, in this study, we optimized Device capping layer at unoptimized micro-cavity structure TEOLED device. And we compare only capping layer with unoptimized microcavity structure can overcome optimized micro-cavity structure device. We used previous our optimized micro-cavity structure to compare each other. As a result, it has been found that the efficiency can be obtained almost the same or higher only capping layer, which is stacked on top of the device and controls only the thickness and refractive index, without complicated structural calculations. This means that higher efficiencies can be obtained more easily in laboratories with limited organic materials or when optimizing new structures etc.

The Study of Dielectric Layer Design for Luminance Efficiency of White Organic Light Emitting Device (백색 OLED의 발광효율 향상을 위한 Dielectric Layer 설계에 관한 연구)

  • Kim, Sang-Gi;Jin, En Mei;Gu, Hal-Bon
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.10
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    • pp.850-853
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    • 2009
  • We have optimized the device structure by using the dielectric layer such as anti-reflection thin film to improve the emitting efficiency of white organic light emitting device (WOLED). Basically, dielectric layer with anti-reflection characteristics can enhance the emitting efficiency of WOLED by compensating the refractive index of organic layer, ITO, and Glass. Here, WOLED was designed and optimized by Macleod simulator. The refractive index of 1.74 was calculated for Dielectric layer and was selected as $TiO_2$. The optimal thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively, at the wavelength of 600 nm. The transmittance of ITO was measured with the thickness variation of dielectric layer and ITO in Organic layer/ITO/Dielectric layer structure. The transmittance of ITO was 95.17% and thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively. This result, calculated and measured values were coincided.

The effects of buffer layer using $\alpha$-septithiophene on the organic light emitting diode (유기 전기 발광 소자에서 $\alpha$-septithiophene을 이용한 buffer layer의 영향)

  • Yi, Ki-Wook;Lim, Sung-Taek;Shin, Dong-Myung;Park, Jong-Wook;Park, Ho-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.04b
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    • pp.53-56
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    • 2002
  • The effect of $\alpha$-septithiophene (${\alpha}-7T$) layers on the organic light emitting diode(OLED) was studied. The ${\alpha}-7T$ was used for a buffer layer in OLED. Hole injection was investigated and improved emission efficiency. The OLEDs structure can be described as indium tin oxide(ITO)/ buffer layer / hole transporting layer / emitting layer / electron transporting layer / LiF / Al. The hole transporting layer were composed of N,N-diphenyl-N,N-di(3-methylphenyl)-1,1-biphenyl-4,4-diamine(TPD), and N,N-di(naphthalene-1-ly)-N,N-diphenyl-benzidine( ${\alpha}$-NPD). The emitting layer, and electron transporting layer consist of tris(8-hydroxyquinolinato) aluminum($Alq_3$). All organic layer were deposited at a background pressure of less than $10^{-6}$ torr using ultra high vacuum (UHV) system. The ${\alpha}-7T$ layer can substitute the hole blocking layer, and improve hole injection properties.

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Effects of Buffer Layer in Organic Light-Emitting Diodes Using Poly(N-vinylcarbazole)

  • Chung, Dong-Hoe;Hong, Jin-Woong;Kim, Tae-Wan
    • Journal of the Korean Applied Science and Technology
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    • v.20 no.2
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    • pp.173-176
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    • 2003
  • We have seen the effects of buffer layer in organic light-emitting diodes using poly(N-vinylcarbazole)(PVK). Polymer PVK buffer layer was made using static spin-casting method. Two device structures were made; one is ITO/TPD/Alq3/Al as a reference and the other is ITO/PVK/TPD/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage characteristics, luminance-voltage characteristics and luminous efficiency were measured with a variation of spin-casting speeds. We have obtained an improvement of luminous efficiency by a factor of two and half when the PVK buffer layer is used.

A Study on Electric Characteristics of Multi-layer by Light Organic Emitting Diode (유기발광소자(Organic Light Emitting Diode)의 다층박막에 대한 전기적 특성 연구)

  • Lee Jung-Ho
    • Journal of Korea Society of Industrial Information Systems
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    • v.10 no.2
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    • pp.76-81
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    • 2005
  • This research approached electrical characteristics of organic light emitting diodes getting into the spotlight by next generation display device. Basic mechanism of OLED's emitting is known as that electron by cathode of lower work function and hole by anode of higher work function are driven and recombine exciton-state being flowed in emitting material layer passing carrier transport layer In order to make many electron-hole pairs, we must manufacture device in multi-layer structure. There are Carrier Injection Layer(CIL), Carrier Transport Layer(CTL) and Emitting Material Layer(EML) in multi-layer structure. It is important that regulate thickness of layer for high luminescence efficiency and set mobility of hole and electron.

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Correlation between optimized thicknesses of capping layer and thin metal electrode for efficient top-emitting blue organic light-emitting diodes

  • Hyunsu Cho;Chul Woong Joo;Byoung-Hwa Kwon;Chan-mo Kang;Sukyung Choi;Jin Wook Sin
    • ETRI Journal
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    • v.45 no.6
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    • pp.1056-1064
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    • 2023
  • The optical properties of the materials composing organic light-emitting diodes (OLEDs) are considered when designing the optical structure of OLEDs. Optical design is related to the optical properties, such as the efficiency, emission spectra, and color coordinates of OLED devices because of the microcavity effect in top-emitting OLEDs. In this study, the properties of top-emitting blue OLEDs were optimized by adjusting the thicknesses of the thin metal layer and capping layer (CPL). Deep blue emission was achieved in an OLED structure with a second cavity length, even when the transmittance of the thin metal layer was high. The thin metal film thickness ranges applicable to OLEDs with a second microcavity structure are wide. Instead, the thickness of the thin metal layer determines the optimized thickness of the CPL for high efficiency. A thinner metal layer means that higher efficiency can be obtained in OLED devices with a second microcavity structure. In addition, OLEDs with a thinner metal layer showed less color change as a function of the viewing angle.

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.

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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Development of Blue Organic Light-emitting Diodes(OLEDs) Due to Change in Mixed Ratio of HTL:EML(DPVBi:NPB) Layers (HTL:EML(DPVBi:NPB)층의 조성비 변화에 따른 청색 유기 발광 소자 개발)

  • Lee, Tae-Sung;Lee, Byoung-Wook;Hong, Chin-Soo;Kim, Chang-Kyo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.21 no.9
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    • pp.853-858
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    • 2008
  • The structure of organic light-emitting diodes(OLEDs) with typical heterostructure consists of anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. 4,4bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl(NPB) used as a hole transport layer and 4'4-bis(2,2'-diphenyl vinyl)-1,1'-biphenyl(DPVBi) used as a blue light emitting layer were graded-mixed at selected ratio. Interface at heterojunction between the hole transport layer and the elecrtron transport layer restricts carrier's transfer. Mixing of the hole transport layer and the emitting layer reduces abrupt interface between the hole transport layer and the electron transport layer. The operating voltage of OLED devices with graded mixed-layer structure is 2.8 V at 1 $cd/m^2$ which is significantly lower than that of OLED device with typical heterostructure. The luminance of OLED devices with graded mixed-layer structure is 21,000 $cd/m^2$ , which is much higher than that of OLED device with typical heterostructure. This indicates that the graded mixed-layer enhances the movement of carriers by reducing the discontinuity of highest occupied molecular orbital(HOMO) of the interface between hole transport layer and emitting layer.