• 제목/요약/키워드: Light-emitting diodes

검색결과 1,318건 처리시간 0.034초

High-performance InGaN/GaN-based Light-emitting Diodes Using Advanced Technical Approaches

  • Jang, Ja-Soon
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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    • pp.108-108
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    • 2012
  • High-performance GaN-based light emitting diodes (LEDs) with high efficiency and excellent reliability have been of technological importance forapplications in full color display, automotive lighting, and solid state lighting. To realize high-performance and excellent-reliability LEDs, various technologies such as surface texturing, transparent conducting oxide, surface Plasmon, highly p-conduction layer, current blocking layer, photon-enhanced layer, and nanostructures have been extensively investigated. Among them, advanced core technologies based on how to suppress surface leakage and current crowding, how to enhance current injection efficiency and output power, and how to resist electrostatic damage will be displayed and discussed using our reported and preliminary results. New approaches like integrated LEDs will be also introduced and discussed.

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Ba/Ag 투명 음극을 이용한 전면발광 OLEDs의 전기 및 광학적 특성 (Electrical and Optical Properties of Top Emission OLEDs with Ba/Ag Transparent Cathodes)

  • 문대규;이찬재;한정인
    • 한국전기전자재료학회논문지
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    • 제19권9호
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    • pp.873-877
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    • 2006
  • We have fabricated top omission organic light emitting diodes with transparent Ba/Ag double layer cathodes deposited by using thermal evaporation method. The device structure was $glass/Ni(200nm)/2-TNATA(15 nm)/{\alpha}-NPD(15nm)Al_{q3}:C545T\;(1%,\;35nm)/BCP(5nm)/Ba(10nm)/Ag(8nm)$. The optical transmittance of the Ba(10 nm)/Ag(8 nm) layer was over 60 % in the visible wavelength region. The maximum efficiency of the device was $13.7\;cd/A\;at\;0.69\;mA/cm^{2}$ and the efficiency of over 10 cd/A was achieved at wide range of current densities and luminances.

Differences in Design Considerations between InGaN and Conventional High-Brightness Light-Emitting Diodes

  • Lee, Song-Jae
    • Journal of the Optical Society of Korea
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    • 제2권1호
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    • pp.13-21
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    • 1998
  • Based on the escape cone concepts, high-brightness light-emitting diodes (LEDs) have been analyzed. In AlGaAs or InGaAlP LEDs, photon absorption in the ohmic region under the electrode is known to be significant. Thus, ins general, a thick window layer (WL) and a transparent substrate (TS) would minimize photon shielding by the electrodes and considerably improve photon output coupling efficiency. However, the schemes do not seem to be necessary in InGaN system. Photon absorption in ohmic contact to a wide bandgap semiconductor such as GaN may be negligible and, as a result, the significant photon shielding by the electrodes will not degrade the photon output coupling efficiency so much. The photon output coupling efficiency estimated in InGaN LEDs is about 2.5 - 2.8 times that of the conventional high-brightness LED structures based on both WL and TS schemes. As a result, the extenal quantum efficiency in InGaN LEDs is as high as 9% despite the presumably very low internal quantum efficiency.

Fabrication Process of Light Emitting Diodes Using CdSe/CdS/ZnS Quantum Dot

  • Cho, Nam Kwang;Kang, Seong Jun
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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    • pp.428-428
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    • 2013
  • Red color light emitting diodes were fabricated using CdSe/CdS/ZnS quantum dots (QDs). Patterned indium-tin-oxide (ITO) was used as a transparent anode, and oxygen plasma treatment on a surface of ITO was performed. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was spin coated on the ITO surface as a hole injection layer. Then CdSe/CdS/ZnS QDs was spin coated and thermal treatment was performed for the cross-linking of QDs. TiO2 was coated on the QDs as an electron transport layer, and 150 nm of aluminum cathode was formed using thermal evaporator and shadow mask. The device shows a pure red color emission at 606 nm wavelength. Device characteristics will be presented in detail.

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Tandem white organic light emitting diodes comprising of red, green, blue emission

  • Yang, Jung-Jin;Suman, C.K.;Lee, Chang-Hee
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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    • pp.820-822
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    • 2009
  • Tandem white organic light emitting diodes (WOLEDs) are fabricated by using a transparent interconnecting layer of Al:LiF composite/molybdenum oxides ($MoO_3$). We demonstrate two types of tandem WOLEDs consisting of two color emissions (red and blue emission) and three color emissions (red, green and blue emission). Tandem WOLED consisting of three color emission shows higher external quantum efficiency and current efficiency.

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Improved stability of organic light-emitting diodes with lithium-quinolate doped electron transport layer

  • Choi, Sung-Hoon;Kim, Sang-Dae;Han, Kyu-Il;Lee, Se-Hee;Park, Eun-Jung;Kum, Tae-Il;Jung, Young-Kwan;Lee, Seok-Jong;Lee, Nam-Yang
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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    • pp.771-774
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    • 2009
  • The Improved stability of organic light emitting diodes (OLEDs) containing lithium-quinolate (Liq) as the ETL doping material is investigated. The lifetime could be improved by threefold using the Liq-doped ETL structure. The improvement was attributed to the Liq-doped ETL, which improved hole-electron balance and has a good electrical stability. Additionally, when the Liq doped device was combined with an Mg/Al cathode, the OLED produced a longer lifetime than other device.

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Development of an alignment free mask patterning as a new fabrication method for high efficiency white organic light-emitting diodes

  • Joo, Chul-Woong;Jeon, Soon-Ok;Yook, Kyoung-Soo;Lee, Jun-Yeob
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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    • pp.752-754
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    • 2009
  • High efficiency white organic light emitting diodes were fabricated by using an alignment free mask patterning method. Only red/green emission without any blue emission was observed in the red/green patterned region and blue emission was emitted in other area. A combination of the red/green and blue emission gave a high efficiency white emission. A maximum current efficiency of 30.7 cd/A and a current efficiency of 25.9 cd/A at 1000 cd/$m^2$ were obtained with a color coordinate of (0.38, 0.45).

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Passivation of organic light emitting diodes with a-$SiN_x$ thin films grown by catalyzer enhanced chemical vapor deposition

  • Jeong, Jin-A;Kang, Jae-Wook;Kim, Han-Ki
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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    • pp.659-662
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    • 2007
  • The characteristics of a $SiN_x$ passivation layer grown by a specially designed catalyzer enhanced chemical vapor deposition (CECVD) system and electrical and optical properties of OLEDs passivated with the $SiN_x$ layer are described. Despite the low substrate temperature, the single $SiN_x$ passivation layer, grown on the PC substrate, exhibited a low water vapor transmission rate of $2{\sim}6{\times}10^{-2}\;g/m^2/day$ and a high transmittance of 87 %. In addition, current-voltage-luminescence results of an OLED passivated with a 150 nm-thick $SiN_x$ film compared to nonpassivated sample were identical indicating that the performance of an OLED is not critically affected by radiation from tungsten catalyzer during the $SiN_x$ deposition.

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Numerical Analysis Using Finite Element Method On Phosphorescent Organic Light Emitting Diodes

  • Hwang, Y.W.;Lee, H.G.;Won, T.Y.
    • JSTS:Journal of Semiconductor Technology and Science
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    • 제14권1호
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    • pp.29-33
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    • 2014
  • In this paper, we report our numerical simulation on the electronic-optical properties of the phosphorescent organic light emitting diodes (PHOLEDs) devices. In order to calculate the electrical and optical characteristics such as the transport behavior of carriers, recombination kinetics, and emission property, we undertake the finite element method (FEM). Our model includes Poisson's equation, continuity equation to account for behavior of electrons and holes and the exciton continuity/transfer equation. We demonstrate that the refractive indexes of each material affect the emission property and the barrier height of the interface influences the behavior of charges and the generation of exciton.

고출력 형광체변환 백색 LED 패키지의 가속시험 (Acceleration Test for Package of High Power Phosphor Converted White Light Emitting Diodes)

  • 천성일;윤양기;장중순
    • 한국신뢰성학회지:신뢰성응용연구
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    • 제10권2호
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    • pp.137-148
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    • 2010
  • This study deals with the accelerated life test of high power phosphor converted white Light Emitting Diodes (High power LEDs). Samples were aged at $110^{\circ}C$/85% RH and $130^{\circ}C$/85% RH up to 900 hours under non-biased condition. The stress induced a luminous flux decay on LEDs in all the conditions. Aged devices exhibited modification of package silicon color from white to yellowish brown. The instability of the package contributes to the overall degradation of optical lens and structural degradations such as generating bubbles. The degradation mechanisms of lumen decay and reduction of spectrum intensity were ascribed to hygro-mechanical stress which results in package instabilities.