• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.107-111
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• 2013

A new green-emitting material with donor-acceptor architecture, 3,7-bis(1'-phenylbenzimidazole-2'-yl)-10-phenylphenothiazine (BBPP) was synthesized and its thermal, optical, and electroluminescent characteristics were investigated. Organic light-emitting diodes (OLEDs) with four different multilayer structures were prepared using BBPP as an emitting layer. The optimized device with the structure of [ITO/2-TNATA (40 nm)/BBPP (30 nm)/TPBi (30 nm)/Alq3 (10 nm)/LiF (1 nm)/Al (100 nm)] exhibited efficient green emission. Enhanced charge carrier balance and electron mobility in the organic layers enabled the device to demonstrate a maximum luminance of 31,300 cd/$m^2$, a luminous efficiency of 6.83 cd/A, and an external quantum efficiency of 1.62% with the CIE 1931 chromaticity coordinates of (0.21, 0.53) at a current density of 100 mA/$cm^2$.

• Journal of Information Display
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• 제4권1호
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• pp.29-33
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• 2003

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of $ITO/bufferr/TPD/Alq_3/Al$. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1293-1294
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• 2006

OLEDs based on organic thin films are similar to semiconductor base light-emitting diodes in that they were also considered to be one of the next generation flat-panel displays. They are attractive because of low-operating voltage, low power consumption, ease of fabrication, and low cost. In this study, we used poly (3,4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PE DOT : PSS) as a hole injection layer. In this experiment spin coating method was used with various speed rate. The fundamental structure of the OLEDs was ITO/PEDOT:PSS/NPB/$Alq_3$/Al. As a result, we obtained the enhancement performance of OLEDs when the spin coating speed was 4000 rpm. We obtained a maximum luminance of 24334 $cd/m^2$ at a current density of 967 $mA/cm^2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 학술대회 및 기술세미나 논문집 디스플레이 광소자
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• pp.49-51
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• 2006

OLEOs was fabricated by PLD method. Wet etching process and plasma treatment of ITO on the glass were performed to extend the lifetime of the OLED and increase its brightness. The NPB, $Alq_3$, Li-Benzoate and AI layers on ITO pattern on the glass were deposited by PLO method, sequentially. When the etched ITO was treated by $O_2$ plasma with RF power of 50W, the best result was obtained. The lifetime of the OLED treated by $O_2$ plasma was extended from 3,770sec to 12,586sec compared to that without the plasma treatment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.428-429
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• 2006

In this thesis, verifies electrical-optical characteristics of phosphorescent materials. basic structure of fabricating devices is glass/ITO/$\alpha$-NPD($300{\AA}$)/CBP:Guest($300{\AA}$)/BCP($80{\AA}$)/$Alq_3(100{\AA})$/Al($1000{\AA}$). In efficiency, fabrication of organic light emitting diodes using $Ir(btp)_2acac$ phosphorescent material is external quantum efficiency 0.268% as doping concentration 3%. At CIE coordinates, phosphorescent material $Ir(btp)_2acac$ following materials moves high purity red color(x=0.6686, y=0.3243). The brightness shows $285cd/cm^2$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.424-424
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• 2010

유기발광소자는 전류구동소자로서 소자를 대형화할 때 소모 전력이 급격히 증가하여 다른 디스플레이 제품에 비해 더욱 더 높은 전력효율을 요구한다. 높은 전력효율과 낮은 구동전압을 갖는 유기발광소자를 제작하기 위해서 P-I-N구조의 유기발광소자에 관한 연구가 활발히 진행되고 있다. 본 연구에서는 일함수가 큰 투명 Indium Tin Oxide (ITO) 양극 위에 p 형 불순물인 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) 를 4,4',4"-tris(N-(2naphthyl)-N-phenylamino)triphenylamine (2-TNATA)에 도핑하여 정공주입 및 정공수송을 향상하였으며, 그위에 N,N'-bis(1-naphthyl)-N,N'-diphenyl- 1,1'-biphenyl-4,4'-diamine (NPB) 층을 증착 후, tris-(8-hydroxyquinoline) aluminum ($Alq_3$) 발광층과 전자 수송층으로 사용하여 전자와 정공이 재결합을 하여 엑시톤을 형성하여 녹색 빛을 측정하였다. p 형 불순물은 정공 수송층의 에너지 장벽을 감소하며 발광층으로의 정공주입량을 증가하는 역할을 하여 구동전압을 감소하였으나 발광층내에서 전자와 정공의 비를 불균일하게 하여 발광효율은 약간 감소하였다. p형 불순물인 F4-TCNQ의 도핑의 농도에 따라 측정된 발광특성의 변화로부터 정공의 전송 메카니즘을 분석하였으며 이는 p형 불순물 첨가된 녹색 유기발광소자의 전하수송 메카니즘을 이해하는데 중요한 자료를 제공할 것이다.

• 반도체디스플레이기술학회지
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• 제21권3호
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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.

• Transactions on Electrical and Electronic Materials
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• 제13권2호
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• pp.60-63
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• 2012

Enhancement of efficiency and luminance of organic light-emitting diodes was investigated by the introduction of a lithium carbonate ($Li_2CO_3$) electron-injection layer. Electron-injection layer is used in organic light-emitting diodes to inject electrons efficiently between a cathode and an organic layer. A device structure of ITO/TPD (40 nm)/$Alq_3$ (60 nm)/$Li_2CO_3$ (x nm)/Al (100 nm) was manufactured by thermal evaporation, where the thickness of $Li_2CO_3$ layer was varied from 0 to 3.3 nm. Current density-luminance-voltage characteristics of the device were measured and analyzed. When the thickness of $Li_2CO_3$ layer is 0.7 nm, the current efficiency and luminance of the device at 8.0 V are improved by a factor of about 18 and 3,000 compared to the ones without the $Li_2CO_3$ layer, respectively. The enhancement of efficiency and luminance of the device with an insertion of $Li_2CO_3$ electron-injection layer is thought to be due to the lowering of an electron barrier height at the interface region between the cathode and the emissive layer. This is judged from an analysis of current density-voltage characteristics with a Fowler-Nordheim tunneling conduction mechanism model. In a study of lifetime of the device that depends on the thickness of $Li_2CO_3$ layer, the optimum thickness of $Li_2CO_3$ layer was obtained to be 1.1 nm. It is thought that an improvement in the lifetime is due to the prevention of moisture and oxygen by $Li_2CO_3$ layer. Thus, from the efficiency and lifetime of the device, we have obtained the optimum thickness of $Li_2CO_3$ layer to be about 1.0 nm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1712-1714
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• 2004

During the last 20 years organic semiconductors have attracted considerable attention due to their interesting physical properties followed by various technological applications in the area of electronics and opto-electronics. It has been a long time since organic solar cells were expected as a low-cost energy-conversion device. Although practical use of them has not been achieved, technological progress continues. Morphology of the materials, organic/inorganic interface, metal cathodes, molecular packing and structural properties of the donor and acceptor layers are essential for photovoltaic response. We have fabricated solar cell devices based on zinc-phthalocyanine(ZnPc) as donor(D) and fullerine($C_{60}$) as electron acceptor(A) with doped charge transport layers, $Alq_3$ as an electron transport or injection layer. We observed the photovoltaic characteristics of the solar cell devices using the Xe lamp as a light source.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.168-169
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• 2009

본 연구에서는 ITO 표면 개질에 의한 유기 발광 소자의 특성 변화에 대해서 연구하였다. ITO 전극은 발광 소자의 투명 전극으로 널리 사용되고 있으며 이러한 발광 소자의 특성은 ITO의 표면 상태에 따라 민감하게 반응한다. ITO 표면 개질은 ITO와 유기물 사이의 쇼트기 장벽을 감소시키며, 전극과 유기물의 점착을 향상시켜 준다. 본 실험에서는 습식 처리 방식으로 self-assembled monolayer(SAM)을 사용하였다. 유기 발광 소자의 특성은 SAM 처리에 의해 향상 되었다. 유기 발광 소자는 ITO/SAM/TPD(50nm)/$Alq_3$(70nm)/LiF(0.5nm)/Al(100nm)의 구조로 제작하였으며, ITO의 표면 특성은 일반적인 특성 기술에 의해 연구되었다. SAM 처리된 소자는 SAM 처리하지 않은 소자에 비해 구동 전압, 발광 세기, 외부 양자 효율 등이 향상되었다. ITO의 SAM 처리 시간을 0/10/15/20/25분으로 하여 소자를 제작하였다. 15분간 SAM 처리한 소자는 SAM 처리하지 않은 소자에 비해 외부 양자 효율과 전류 효율이 2.6배 상승하였다. 본 실험을 통하여 ITO 표면 위에 SAM층을 삽입한 걸과, 구동 전압, 발광 세기, 효율 등이 향상됨을 알 수 있었다.