• Title/Summary/Keyword: Top Emission

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Organic-layer and reflectivity of transparent electrode dependent, microcavity effect of top-emission organic light-eitting diodes (TE-OLED의 유기물층과 반투명 음전극의 반사도에 따른 마이크로 캐비티 특성)

  • An, Hui-Chul;Na, Su-Hwan;Joo, Hyun-Woo;Mok, Rang-Kyun;Jung, Kyung-Seo;Chio, Seong-Jea;Kim, Tae-Wan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.299-300
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    • 2009
  • We have studied an organic layer and semitransparent Al cathode thickness dependent optical properties for top-emission organic light-emitting diodes. Device structure is ITO(170nm)/TPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(100nm) and Al(100nm)/TPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(25nm). While a thickness of total, organic layer was varied from 85nm to 165nm, a ratio of those two layers was kept to be about 2:3. Then it was compared with that of bottom devices. And a thickness of semitransparent Al cathode was varied from 20nm to 30nm for the device with an organic layer thickness of 140nm. We were able to control the emission spectra from the top-emission organic light-emitting diodes.

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Top-emission Electroluminescent Devices based on Ga-doped ZnO Electrodes (Ga-doped ZnO 투명전극을 적용한 교류무기전계발광소자 특성 연구)

  • Lee, Wun Ho;Jang, Won Tae;Kim, Jong Su;Lee, Sang Nam
    • Journal of the Semiconductor & Display Technology
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    • v.16 no.2
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    • pp.44-48
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    • 2017
  • We explain optical and electrical properties of top and bottom-emission structured alternating-current powder electroluminescent devices (ACPELDs) with Ga-doped ZnO(GZO) transparent electrode. The top-emission ACPELDs were layered as the metal electrode/dielectric layer/emission layer/top transparent electrode and the bottom-emission ACPELDs were structured as the bottom transparent electrode/emission layer/dielectric layer/metal electrode. The yellow-emitting ZnS:Mn, Cu phosphor and the barium titanate dielectric layers were layered through the screen printing method. The GZO transparent electrode was deposited by the sputtering, its sheet resistivity is $275{\Omega}/{\Box}$. The transparency at the yellow EL peak was 98 % for GZO. Regardless of EL structures, EL spectra of ACPELDs were exponentially increased with increasing voltages and they were linearly increased with increasing frequencies. It suggests that the EL mechanism was attributed to the impact ionization by charges injected from the interface between emitting phosphor layer and the transparent electrode. The top-emission structure obtained higher EL intensity than the bottom-structure. In addition, charge densities for sinusoidal applied voltages were measured through Sawyer-Tower method.

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A Study on the Effects of Micro Cavity on the HTL Thicknesses on the Top Emission Organic Light Emitting Diode (유기발광 다이오드의 정공수송층 두께에 따른 미소 공진 효과의 영향에 관한 연구)

  • Lee, DongWoon;Cho, Eou Sik;Seong, Jin-Wook;Kwon, Sang Jik
    • Journal of the Semiconductor & Display Technology
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    • v.21 no.1
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    • pp.91-94
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    • 2022
  • Top emission organic light-emitting diode is commonly used because of high efficiency and good color purity than bottom - emission organic light-emitting device. Unlike BEOLED, TEOLED contain semi-transparent metal cathode. Because of semi-transparent cathode, micro cavity effect occurs in TEOLED. We optimized this effect by changing the thickness of hole injection layer. Device consists of is indium-tin-oxide / N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (x nm) / tris-(8-hydroxyquinoline) aluminum (50nm) / LiF(0.5nm) / Mg:Ag (1:9), and we changed NPB thickness which is used as HTL in our device in order to study how micro cavity effects are changed by optical path. As the results, NPB thickness at 35nm showed the current efficiency of 8.55Cd/A.

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Optimization of Mg:Ag Cathodes and Effect of LiF Electron Injection Layer on the Characteristics of Top Emission Organic Light Emitting Diodes (전면 유기발광 다이오드 제작시 Mg:Ag 캐소드 최적화 및 LiF 전자주입층 유무에 따른 소자 특성에 관한 연구)

  • Song, Min Seok;Kwon, Sang Jik;Cho, Eou-Sik
    • Journal of the Semiconductor & Display Technology
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    • v.21 no.1
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    • pp.71-74
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    • 2022
  • For the process simplification in the fabrication of organic light emitting diode(OLED), top emission OLED (TEOLED) was fabricated without lithium fluoride(LiF) used as an electron injection layer (EIL). After co-deposition of Mg and Ag with a different process conditions, a cathode material adjacent to EIL was optimized when Mg and Ag have a ratio of 1:9 considering sheet resistance and transmittance. From the energy band diagram of TEOLED, band gap difference between Trisaluminium (Alq3) and Mg:Ag cathode show the difference of 0.4 eV according to the usage of LiF The fabricated TEOLED without LiF showed the improvement of 5.2 % and 2.7 % in the luminance and the current density comparing that with LiF. The results show there is no significant difference in OLED characteristics regardless of LIF layer in the TEOLED structures.

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High reflective anode for top emission OLED

  • Pang, Hee-Suk;Han, Chang-Wook;Kim, Ki-Yong;Chung, In-Jae
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.820-823
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    • 2004
  • We present high reflective anode for top emission OLED. Anode consists of two layers, which are increasing the ability of hole injection and the reflectivity of emitted light. Thin Cr is deposited on AlNd that has a high thermal resistance and reflectivity. The current-voltage characteristics of Cr(30${{\AA}}$)/AlNd(1000${{\AA}}$) anode are poor but these of Cr(50${{\AA}}$)/AlNd(1000${{\AA}}$) anode are superior to these of Cr(30${{\AA}}$)/AlNd(1000${{\AA}}$) and the work function of cr(50${{\AA}}$)/AlNd(1000${{\AA}}$) is higher that of Cr(30${{\AA}}$)/AlNd(1000${{\AA}}$).

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Development of a 14.1 inch Full Color AMOLED Display with Top Emission Structure

  • Jung, J.H.;Goh, J.C.;Choi, B.R.;Chai, C.C.;Kim, H.;Lee, S.P.;Sung, U.C.;Ko, C.S.;Kim, N.D.;Chung, K.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07a
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    • pp.793-796
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    • 2005
  • A structure and a design of device were developed to fabricate large-scale active matrix organic light-emitting diode (AMOLED) display with good color purity and high aperture ratio. With these technologies, we developed a full color 14.1 inch WXGA AMOLED display. For the integration of OLED on an active matrix a-Si TFT backplane, an efficient top emission OLED is essential since the TFT circuitry covers a large position of the pixel aperture. These technologies will enable up the OLED applications to larger size displays such as desktop monitors and TVs.

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

  • Moon, Dae-Gyu;Lee, Chan-Jae;Han, Jeong-Inn
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.9
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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.

Long-lifetime Green Phosphorescent OLEDs for Low Power Displays

  • Weaver, Michael S.;Adamovich, Vadim I.;Xia, Sean C.;Fiordeliso, James J.;Kwong, Raymond C.;Brown, Julie J.;Lee, Kwan-Hee;Lim, Choon-Woo;Kim, Sung-Chul
    • 한국정보디스플레이학회:학술대회논문집
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    • 2009.10a
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    • pp.38-41
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    • 2009
  • We demonstrate a new commercial green phosphorescent organic light emitting device (OLED) in a bottom emission device and top emission microcavity. The bottom and top emitting phosphorescent OLEDs (PHOLED$^{TM}$s) had luminance efficiencies of 60cd/A and 137cd/A respectively, at a luminance of 1,000cd/$m^2$. The top emission microcavity was close to 1953 NTSC color requirements with 1931 CIE color coordinates of 0.231, 0.718. A record green PHOLED lifetime of >3,500hrs to LT95 from 4000cd/$m^2$ is demonstrated for the microcavity device.

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