• 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.

• 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.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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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.

• Journal of the Semiconductor & Display Technology
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• v.5 no.3 s.16
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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).

• 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.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.23-27
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• 2023

Organic light-emitting diode(OLED) is very thin organic films which are hundreds of nanometers. Unlike bottom-emission OLED(BEOLED), top-emission OLED(TEOLED) emits light out the front, opaque moisture absorbents or metal foils can't be used to prevent moisture and oxygen. And it is difficult to have flexible characteristics with glass encapsulation, so thin film encapsulation which can compensate for those two disadvantages is mainly used. In this study, Al₂O₃ thin films by atomic layer deposition(ALD) were examined by changing the argon gas purge flow rate and we applied this Al₂O₃ thin films to the encapsulation of TEOLED. Ag / ITO / N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine / tris-(8-hydroxyquinoline) aluminum/ LiF / Mg:Ag (1:9) were used to fabricate OLED device. The characteristics such as brightness, current density, and power efficiency are compared. And it was confirmed that with a thickness of 40 nm Al₂O₃ thin film encapsulation process did not affect OLED properties. And it was enough to maintain a proper OLED operation for about 9 hours.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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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.

• Journal of the Semiconductor & Display Technology
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• v.7 no.1
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• pp.47-51
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• 2008

The Al:Au double-layer metal electrode for use in transparent, dual emission of organic light-emitting diode (OLED) was fabricated. The electrode of Al:Au metals with various thicknesses was deposited by the vacuum thermal evaporation technique. For Al thickness of 1 nm, a bottom luminance of $4880\;cd/m^2$ was observed at 8 V. Otherwise, top luminance of $2020\;cd/m^2$ were observed at 8 V. In addition, the threshold voltages of the electrodes were 2.2 V. It was forward that the inserting 1 nm Al between LiF and Au enhanced electron injection with tunneling effect.