• Title/Summary/Keyword: Top emission

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Electrical and Optical Properties of Red Phosphorescent Top Emission OLEDs with Transparent Metal Cathodes (투명 금속 음극을 이용한 전면발광 적색 인광 OLEDs의 전기 및 광학적 특성)

  • Kim, So-Youn;Ha, Mi-Young;Moon, Dae-Gyu;Lee, Chan-Jae;Han, Jeong-In
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.9
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    • pp.802-807
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    • 2007
  • We have developed red phosphorescent top emission organic light-emitting diodes with transparent metal cathodes deposited by using thermal evaporation technique. Phosphorescent guest molecule, BtpIr(acac), was doped in host CBP for the red phosphorescent emission, Ca/Ag, Ba/Ag, and Mg/Ag double layers were used as cathode materials of top emission devices, which were composed of glass/Ni/2TNATA(15 nm)/${\alpha}$-NPD(35 nm)/CBP:BtpIr(acac)(40 nm, 10%)/BCP(5 nm)/$Alq_3$(5 nm)/cathodes. The optical transparencies of these metal cathodes strongly depend on underlying Ca, Ba, and Mg layers. These layers also strongly affect the electrical conduction and emission properties of the red phosphorescent top emission devices.

Characteristics of transparent metal Cathode for top emission organic light emitting diode (Top emission 유기 발광 소자를 위한 투명 금속 cathode 특성 평가)

  • Lee, Chan-Jae;Moon, Dae-Gyu;Han, Jeong-In;Baik, Sung-Ho;Park, No-Hoon;Ju, Soung-Sam
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.107-110
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    • 2003
  • 본 연구에서는 캐소드 방향으로 발광하는 Top emission 소자를 설계 제작하였다. 이를 위하여 반투명한 금속 박막을 제작하여 전기적 특성과 광학적 특성을 비교 평가하였다. 이를 바탕으로 제작한 Top emission 소자를 bottom emission 소자와 비교하였을 때 구동 전압은 다소 높았으며 색좌표 및 스펙트럼이 이동하였는데 이동 정도와 경향성은 파장에 따라 다르게 나타났다

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Characterization of the High Luminance Top Emission Organic Light-emitting Devices (TEOLEDs) Using Dual Cathode Layer (이중 음극층을 이용한 고휘도 전면발광(Top emission) 유기EL소자의 특성평가)

  • Kang, Yoon-Ho;Lee, Su-Hwan;Shin, Dong-Won;Kim, Sung-Jun;Kim, Dal-Ho;Lee, Gon-Sub;Park, Jea-Gun
    • Journal of the Semiconductor & Display Technology
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    • v.5 no.3
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    • pp.23-27
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    • 2006
  • Recently, Top emission organic light-emitting diode (TEOLED) has been attracted by their potential application for the development of flat panel display (FPD). We have fabricated the high luminance top emission organic-emitting diode (TEOLED) using dual cathode layer and three top emitting structure. These devices were characterized by electroluminescence (EL) and current density-voltage (J-V) measurements. After compared it with Au anode structure, luminance of the device using dual anode was better than using without Al device. Consequently, Al layers are very good candidates for a promising electron-injecting buffer layer for top emission light-emitting diode (TEOLED).

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Organic-layer thickness dependent optical properties of top emission organic light-eitting diodes (전면 유기 발광 소자의 유기물층 두께 변화에 따른 광학적 특성)

  • An, Hui-Chul;Joo, Hyun-Woo;Na, Su-Hwan;Kim, Tae-Wan;Hong, Jin-Woong;Oh, Yong-Cheul;Song, Min-Joung
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.413-414
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    • 2008
  • We have studied an organic layer thickness dependent optical properties and microcavity effects for top-emission organic light-emitting diodes. Manufactured top emission device, structure is Al(100nm)ITPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(23nm). While a thickness of hole-transport layer of TPD was varied from 35 to 65nm, an emissive layer thickness of $Alq_3$ was varied from 50 to 100nm for two devices. A ratio of those two layers was kept to about 2:3. Variation of the layer thickness changes a traverse time of injected carriers across the organic layer, so that it may affect on the chance of probability of exciton formation. View-angle dependent emission spectra were measured for the optical measurements. Top-emission devices show that the emission peak wavelength shifts to longer wavelength as the organic layer thickness increases. For instance, it shifts from 490 to 555nm in the thickness range that we used. View-angle dependent emission spectra show that the emission intensity decreases as the view-angle increases. The organic layer thickness-dependent emission spectra show that the full width at half maximum decreases as the organic layer thickness increases. Top emission devices show that the full width at half maximum changes from 90 to 35nm as the organic layer thickness increases. In top-emission device, the microcavity effect is more vivid as the organic layer thickness increases.

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Application of Parylene Passivation for Top Emission Oragnic Light Emitting Diode (Top emission Organic Light Emitting Diode을 위한 Parylene 보호층의 적용)

  • Choi, Sung-Hoon;Lee, Chan-Jae;Moon, Dae-Gyu;Han, Jeong-In;Oh, Myung-Hwan
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.160-163
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    • 2005
  • Top emission OLED 소자의 안정성 위하여 Parylene을 보호층으로 적용하였다. 고분자화 방법을 이용하여 증착된 Parylene은 진공공정상온에서 증착가능하기 때문에 열에 의한 OLED 소자의 열화를 방지하며 높은 광투과율과 우수한 투습습성에 의하여 고효율 장수명을 OLED 소자에 적합하다. Parylene 5 ${\mu}m$ 의 광투과율은 90 %이상 측정 되었으며 투습율은 0.4849 $g/m^2day$로 측정되었다. Parylene의 보호층로서의 영향을 살펴보기 위하여, 보호층이 형성된 소자와 보호층이 형성되지 않은 소자를 제작하여 대기중에서 그 특성을 측정 비교하였다. 두 제작된 top emission OLED 소자는 최대 휘도가 1000 $cd/m^2$ 이상 측정되었으며, parylene 보호층 공정에 의한 소자의 구동 특성 변화는 나타나지 않았다. 대기중에서 초기휘도 200 $cd/m^2$로 측정된 parylene 보호층이 형성된 소자는 수명이 5 이었고, 보호층이 형성되지 않는 소자의 수명에 비하여 2배 이상 증가하였다.

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Thickness and Angle Dependent Microcavity Properties in Top-Emission Organic Light-Emitting Diodes (상부 발광 유기 발광 소자에서 두께와 시야각에 따른 마이크로 캐비티 특성)

  • Lee, Won-Jae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.1
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    • pp.32-35
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    • 2011
  • Top-emission device has a merit of high aperture ratio and narrow emission spectrum compared to that of bottom-emission one. Emission spectra of top-emission organic light-emitting diodes depending on a layer thickness and view angle were analyzed using a theory of microcavity. Device structure was manufactured to be Al (100 nm)/TPD/$Alq_3$/LiF (0.5 nm)/Al (2 nm)/Ag (30 nm). N,N'-diphenyl-N,N'- di (m-tolyl)-benzidine (TPD) and tris (8-hydroxyquinoline) aluminium (Alq3) were used as a hole-transport layer and emission layer, respectively. And a thickness of TPD and Alq3 layer was varied in a range of 40 nm~70 nm and 60 nm~110 nm, respectively. Angle-dependent emission spectrum out of the device was measured with a device fixed on a rotating plate. Since the top-emission device has a property of microcavity, it was observed that the emission spectrum shift to a longer wavelength region as the organic layer thickness increases, and to a shorter wavelength region as the view angle increases. Layer thickness and view-angle dependent emission spectra of the device were analyzed in terms of microcavity theory. A reflectivity of semitransparent cathode and optical path length were deduced.

Top Emission Organic Light Emitting Diode with Transparent Cathode, Ba-Ag Double Layer

  • Lee, Chan-Jae;Moon, Dae-Gyu;Han, Jeong-In
    • Journal of Information Display
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    • v.7 no.3
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    • pp.23-26
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    • 2006
  • We fabricated top emission organic light emitting diode (TEOLED) with transparent metal cathode Barium and Silver bilayer. Very thin Ba/Ag bilayer was deposited on the organic layer by thermal evaporation. This cathode showed high transmittance over 70% in visible range, and the device with a Ba-Ag has a low turn on voltage and good electrical properties.

Recent Progress on Voltage Drop Compensation in Top Emission Organic Light Emitting Diodes (OLED)

  • Jeong, Byoung-Seong
    • Journal of the Semiconductor & Display Technology
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    • v.19 no.1
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    • pp.49-54
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    • 2020
  • The voltage drop due to the thin cathode film at the large size top emission OLED panel was successfully compensated with making electrical contact between thin cathode and anode auxiliary electrode by 355nm wavelength of laser. It was found that the luminance uniformity dramatically increased from around 15% to more than 80% through this electrical compensation between thin cathode and anode auxiliary electrode. Moreover, the removing process for EL materials on the anode auxiliary electrode process by laser was very reliable and stable. Therefore, it is thought that the EL removal method using laser to make electrical contacts is very appropriate to mass production for such a large size top emission OLEDs to obtain high uniformity of luminance.

Transient characteristics of top emission organic light emitting diodes with red phosphorescent (적색 인광 도판트를 이용한 Top emission OLED의 Transient 특성)

  • Lee, Chan-Jae;Moon, Dae-Gyu;Han, Jeong-In
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.153-156
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    • 2005
  • In this study, we have investigated transient properties of top emission organic light emitting diode (OLED) with a red electrophosphorescent dopant. The emission spectrum shows a strong peak at 620 nm accompanied with a small peak at 675 nm in the red region. Time evolution of electrophosphorescence reveals a decay time of 703 ms at a voltage pulse of 5 V in a device with an emitting area of 20 $mm^2$. Rise and delay times vary from 450 to 14 ms and 73 to 3 ms, respectively, as the voltage amplitude increases from 4.5 to 10 V. These results are compared with the red emitting device without an electron injection layer.

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Characteristics of top emission PLED by metal anodes (금속 애노드의 종류에 따른 Top Emission 특성 평가)

  • Lee, Chan-Jae;Moon, Dae-Kyu;Kwak, Min-Gi;Kim, Young-Hoon;Han, Jeong-In
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.968-971
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    • 2002
  • Hole injection characteristics have been investigated with various metal anodes such as Ni, Pt, Cu, and AI for the top emission polymer light emitting diodes (PLEDs). Devices were composed of metal anode, Poly(3,4-ethylenedioxythiophene) doped with polystyrene sultponated acid (PEDT:PSS), poly [2-methoxy-5-(2-ethylhexyoxy)-1,4-phenylene-vinylene] (MEH-PPV) and Al cathode. The hole injection from ITO anode has been also investigated for the comparison. The I-V characteristics of the PLEDs with different metal anodes were measured. The work function of the anode is strongly related to the hole injection of the device. The current density of the device with Ni anode with higher work function was higher than that of the device with ITO or AI anode at the same operating voltage.

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