• 한국전기전자재료학회논문지
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• 제36권4호
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• pp.397-402
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• 2023

We have developed inverted green phosphorescent organic light emitting diodes (OLEDs) using 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and bis(carbazole-9-yl)biphenyl (CBP) hole transport layers. The driving voltage, current efficiency, power efficiency, and emission characteristics of devices were investigated. While the driving voltage for the same current density was about 1~2 V lower in the devices with the TAPC layer, the maximum luminance was higher in the device with the CBP layer. The maximum current efficiency and power efficiency were 3.2 and 2.7 times higher in the device with the CBP layer, respectively. The higher efficiency in the CBP device resulted from the enhanced hole-electron balance although weak parasitic recombination takes place in the CBP hole transport layer.

• 한국전기전자재료학회논문지
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• 제26권10호
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• pp.745-753
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• 2013

Performance of organic light-emitting diodes incorporating microlens array was simulated using a Light Tools software. Use of microlens array can help the light to escape out of the device. We simulated a reference device that is consisted of reflection layer, emissive layer, and flat transparent substrate. And in this reference device, outcoupled efficiency of 22% was obtained. Several shapes of microlens were applied such as hemisphere, trapezoid, cone, and rectangular parallelepiped. The results showed the improvement of outcoupled efficiency of the device with microlens compared to that of the reference one. And from the analyses of the simulated data, the obtained appropriate shape of microlens is hemisphere, and the improvement of the device with hemispherical lens is 57% higher than that of the reference one.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1003-1006
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• 2003

We have investigated the effect of hole-injection buffer layer and cathodes in organic light-emitting diodes u sing poly (3,4-ethylenedioxythiophene) : poly (stylenesulfonate) (PEDOT: PSS) in a device structure of $ITO/PEDOT:PSS/TPD/Alq_3/Cathode$. Polymer PEDOT:PSS buffer layer was made using spin casting method. Current-voltage, luminance-voltage characteristics and efficiency of device were measured at room temperature with a variation of cathode materials. The device with LiF/Al cathode shows an improvement of external quantum efficiency approximately by a factor of ten compared to that of Al cathode only device. Our observation shows that the energy barrier-height in cathode side is important in improving the efficiency of the organic light-emitting diodes.

• 한국전기전자재료학회논문지
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• 제23권7호
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• pp.539-544
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• 2010

We have synthesized new blue electroluminescent polyalkylfluorene-based copolymers [poly(F-co-Py)x:y, where x:y = 99:1 or 95:5 mole ratios] containing the hole-injecting pyrazole derivative [3,3'-(4,6-bis(octyloxy)-1,3-phenylene)bis(1,5-diphenyl-4,5-dihydro-1H-pyrazole] through Ni(0) mediated polymerization, and their electroluminescent properties were investigated. Electroluminescent (EL) devices were fabricated with ITO / PEDOT:PSS (110 nm) / copolymers or PF homopolymer (80 nm) / Ca (50 nm) / Al (200 nm) configuration. Each EL device constructed from the copolymer exhibited significantly enhanced brightness and efficiency compared with a device constructed from the PF homopolymer. The EL device constructed with poly(F-co-Py)99:1 exhibited the highest luminous efficiency and brightness (0.95 cd/A and $2,907\;cd/m^2$, respectively). The achieved luminous efficiency was an excellent result, providing almost a 4-fold improvement on the efficiency obtainable with the a PF homopolymer device. This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arises from the HOMO level (~5.83 eV) of the poly(F-co-Py)99:1 copolymer, which is higher than that of the PF homopolyme (~5.90 eV).

• International Journal of Contents
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• 제2권3호
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• pp.6-10
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• 2006

Small molecule OLED devices were fabricated and the electro-optical characteristics were analyzed. The luminance and color coordinate of the fabricated OLED device were $24,390cd/m^2$ and (x=0.15, y=0.22), respectively. Current efficiency of 6.8 cd/A and power efficiency of 2.4 lm/W were also obtained under DC operating condition. Transient light intensity was also measured by using Si photodiode.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권9호
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• pp.400-406
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• 2003

Efficient electrodes are devised for organic luminescent device(OLED). ITO electrode is treated with $O_2$ plasma. In order to inject hole efficiently, there is proposed the shape of anode that inserted plasma polymerized films as buffer layer between anode and organic layer using thiophene monomer. In the case of device inserted the buffer layer by using the plasma polymerization after $O_2$ plasma processing for ITO transparent electrode, since it forms the stable interface and reduce the moving speed of hole, the recombination of hole and electronic are made in the emitting layer. Therefore it realized the device capability of two times in the aspect of luminous efficiency than the device which do not be inserted the buffer layer. Experiments are limited to the device that has the structure of TPD/$AIq_3$, however, the aforementioned electrodes can similarly applied to the organic luminous device and the Polymer luminous device.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.109-113
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• 2004

Slitting device is equipment to separate spent fuel of 250 mm rod cut pellets and hull in order to supply required $UO_2$ pellets through the dry pulverizing/mixing device. For development of its device, We have analyzed slitting programs so that the existing device is modified an appropriate scale in the advanced spent fuel conditioning process. The results of the analysis, we added the automatic separation function of pellets and hull, After slitting. Also, we have concentrated on reducing the operation time so that the support and the body of a slitting blade could have been established in the single structure to be easily maintained. It is based on a design and manufacture of a testing device and we have performed an efficiency evaluation. We have analyzed the results of efficiency tests of the slitting device and get the specification of the slitting device. we complete the basic design of the slitting device by using of these data. Therefore, We apply to a basic data when manufacturing a slitting device.

• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2899-2905
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• 2011

We have demonstrated that TPyPA can be used as an efficient multi-functional material for OLEDs; hole transporting material (HTL), blue and white-light emitter. The device based on TPyPA as the HTL exhibited an external quantum efficiency of 1.7% and a luminance efficiency of 4.2 cd/A; these values are 40% higher than the external quantum efficiency and luminance efficiency of the NPD-based reference device. The device based on TPyPA as a blue-light emitter exhibited an external quantum efficiency of 4.2% and a luminance efficiency of 5.3 $cdA^{-1}$ with CIE coordinates at (0.16, 0.14), the device based on TPyPA as a white-light emitter exhibited an external quantum efficiency of 3.2% and a luminance efficiency of 7.7 $cdA^{-1}$ with CIE coordinates at (0.33, 0.39). Also, TPyPA-based organic solar cell (OSC) exhibited a maximum power conversion efficiency of 0.35%. TPyPA-based organic thin-film transistors (OTFTs) exhibited highly efficient field-effect mobility (${\mu}_{FET}$) of $1.7{\times}10^{-4}cm^2V^{-1}s^{-1}$, a threshold voltage ($V_{th}$) of -15.9 V, and an on/off current ratio of $8.6{\times}10^3$.

• 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.

• 한국광학회지
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• 제14권3호
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• pp.306-311
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• 2003

본 논문에서는 광전송시스템에서 파장분할다중화 광소자로 사용되는 박막필터형 광소자의 특성 분석 및 평가를 위해 입력광원을 모델링 하였으며 광경로에 대해 광선추적법을 사용하여 전산모의 한 광특성을 실험과 비교, 분석하였다. 그 결과 입력광원에 대한 cell 방식의 모델링이 결합효율의 정확도 및 가우시안 강도분포에 접근성을 볼 때 마이크로 옵틱스형 광소자 분석함에 있어 적합함을 알 수 있다. 박막필터형 광소자에 대한 최적 전산모의 결과 광섬유와 GRIN 렌즈 사이 거리가 0.24mm이며 GRIN 렌즈와 박막필터 사이 거리가 0.25mm일 때 최대 결합효율은 -0.11 ㏈이었으며 동일한 조건에의 실험결과 -0.35 ㏈의 최대 결합효율을 얻었다. 이것은 단심 및 이심페룰, GRIN 렌즈 등과 같은 구성품의 불완전성과 박막필터에 의한 손실을 고려할 때, 전산모의 결과와 매우 일치하는 것으로서 본 연구에서 제안한 입력광원의 모델링을 적용한 전산모의가 박막필터형 광소자의 특성을 예측할 수 있음을 보였다.