• Journal of Information Display
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• 제3권1호
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• pp.6-10
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• 2002

We have synthesized a new green Ir(III) complex fac-tris-(3-methyl-2-phenyl pyridine)iridium(III) $Ir(mpp)_3$ and fabricated phosphorescent polymer light-emitting device using it as a triplet emissive dopant in PVK. $Ir(mpp)_3$ showed absorption centered at 388 nm corresponding to the $^1MLCT$ transition as .evidenced by its extinction coefficient of the order of $10^3{\cdot}$ From the PL and EL spectra of the $Ir(mpp)_3$ doped PVK film, the emission maximum was observed at 523 nm, due to the radiative decay from the $^3MLCT$ state to the ground state, confirming a complete energy transfer from PVK to $Ir(mpp)_3$. The methyl substitution has probably caused a red shift in the absorption and emission spectrum compared to $Ir(mpp)_3$. The device consisting of a 2 % doped PVK furnished 4.5 % external quantum efficiency at 72 $cd/m^2$ (current density of 0.45 $mA/cm^2$ and drive voltage of 13.9 V) and a peak luminance of 25,000 $cd/m^2$ at 23.4 V (494 $mA/cm^2$). This work demonstrates the impact of the presence of a methyl substituent at the 3-position of the pyridyl ring of 2-phenylpyridine on the photophysical and electroluminescence properties.

• 한국항공우주학회지
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• 제38권11호
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• pp.1123-1129
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• 2010

TA-50 항공기에 적용되는 투명체의 편각은 실제목표와 투명체를 통해 조종사가 인식하는 목표와 차이를 유발시켜, 부정확한 조준 및 이로 인한 무장계통의 정확도를 저하시킨다. 이러한 문제를 해결하기 위해 TA-50 항공기에서는 원드실드 투명체의 편각을 실측하여 편각 계수 형태로 항공기의 통합임무시현컴퓨터에 입력, 각도 편차를 보정하여 전방상향 시현기에서 목표물에 정확히 조준되도록 한다. 이러한 작동원리를 실전에 적용하기 위해 본 연구에서는 편각 자동측정장비를 국내 최초 독자적으로 개발하였다. 또한 편각 유도공식 산출 등 개발개념 및 운영 체계와 장비의 신뢰성 검증을 위한 정확성 및 정밀성에 대한 내용을 다룬다. 본 연구를 통해 개발한 장비의 정확성은 최종 판정기준인 1% 미만으로 매우 적합하였으며, 정밀성 또한 최종 판정기준을 모두 만족하여 매우 적합하다는 결과를 얻었다. 본 연구를 통해 개발된 편각 자동측정장비는 우수한 품질로 입증되어 캐노피 투명체의 국방규격에 등재되어 사용되고 있다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1520-1521
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• 2008

There are several ways to demonstrate white organic light emitting diodes (OLEDs) for displays and solid state lighting applications. Among these approaches are the stacked three primary or two complementary colors light-emitting layers, multiple-doped emissive layer, and excimer and exciplex emission [1-10]. We report on white phosphorescent excimer devices by using two light emitting materials based on platinum complexes. These devices showed a peak EQE of 15.7%, with an EQE of 14.5% (17 lm/W) at $500\;cd/m^2$, and a noticeable improvement in both the CIE coordinates (0.381, 0.401) and CRI (81). Devices with the structure ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 12% FPt (10 nm) /26 mCPy: 2% Pt-4 (15 nm)/BCP (40 nm)/CsF/Al [device 1], ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 2% Pt-4 (15 nm)/26 mCPy: 12% FPt (10 nm)/BCP (40 nm)/CsF/Al [device 2], and ITO/PEDOT:PSS/TCTA (30 nm)/26 mCPy: 2% Pt-4: 12% FPt (25 nm)/BCP (40 nm)/CsF/Al [device 3] were fabricated. In these cases, the emissive layer was either the double-layer of 26 mCPy:12% FPt and 15 nm 26 mCPy: 2% Pt-4, or the single layer of 26mCPy with simultaneous doping of Pt-4 and FPt. Device characterization indicates that the CIE coordinates/CRI of device 2 were (0.341, 0.394)/75, (0.295, 0.365)/70 at 5 V and 7 V, respectively. Significant change in EL spectra with the drive voltage was observed for device 2 indicating a shift in the carrier recombination zone, while relatively stable EL spectra was observed for device 1. This indicates a better charge trapping in Pt-4 doped layers [10]. On the other hand, device 3 having a single light-emitting layer (doped simultaneously) emitted a board spectrum combining emission from the Pt-4 monomer and FPt excimer. Moreover, excellent color stability independent of the drive voltage was observed in this case. The CIE coordinates/CRI at 4 V ($40\;cd/m^2$) and 7 V ($7100\;cd/m^2$) were (0.441, 0.421)/83 and (0.440, 0.427)/81, respectively. A balance in the EL spectra can be further obtained by lowering the doping ratio of FPt. In this regard, devices with FPt concentration of 8% (denoted as device 4) were fabricated and characterized. A shift in the CIE coordinates of device 4 from (0.441, 0.421) to (0.382, 0.401) was observed due to an increase in the emission intensity ratio of Pt-4 monomer to FPt excimer. It is worth noting that the CRI values remained above 80 for such device structure. Moreover, a noticeable stability in the EL spectra with respect to changing bias voltage was measured indicating a uniform region for exciton formation. A summary of device characteristics for all cases discussed above is shown in table 1. The forward light output in each case is approximately $500\;cd/m^2$. Other parameters listed are driving voltage (Bias), current density (J), external quantum efficiency (EQE), power efficiency (P.E.), luminous efficiency (cd/A), and CIE coordinates. To conclude, a highly efficient white phosphorescent excimer-based OLEDs made with two light-emitting platinum complexes and having a simple structure showed improved EL characteristics and color properties. The EQE of these devices at $500\;cd/m^2$ is 14.5% with a corresponding power efficiency of 17 lm/W, CIE coordinates of (0.382, 0.401), and CRI of 81.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1133-1136
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• 1995

RF-magnetron sputtering 방법으로 형성한 $BaTa_2O_6$의 공정변수에 따른 전기, 광학적 특성변화를 관찰하여 $BaTa_2O_6$ 박막의 TFELD(thin film electroluminescent display) 절연막으로서 응용 가능성을 연구하였다. $BaTa_2O_6$ 박막의 유전특성은 증착시의 $O_2$ 함량과 sputtering 압력의 변화에는 큰 영향을 받지 않으나 기판온도에는 영향을 받는 것으로 확인되었다. 이들 공정변수를 가변하여 실험한 결과, $BaTa_2O_6$ 박막 형성의 최적조건으로 플라즈마 압력을 6 mtorr, sputtering gas 내의 $O_2$ 혼합비율은 40%, 기판온도는 $100^{\circ}C$로 결정하였다. 이상의 조건에서 제조된 $BaTa_2O_6$ 박막은 10.2 ${\mu}C/cm^2$의 매우 우수한 성능지수를 보였다. 이상의 $BaTa_2O_6$ 박막을 하부절연층으로, 절연파괴강도가 높은 $SiO_xN_y$를 상부 절연층으로 사용하여 제조된 EL 소자는 1 kHz, 삼각파 구동시 발광 임계전압은 약 32 volts, 최대휘도는 54 $cd/m^2$으로 측정되었다.

• 한국인쇄학회지
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• 제28권1호
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• pp.51-63
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• 2010

Ink-jet is part of the non impact printing that shooting the ink drop from the nozzle to paper. It is very silence and express good color. There are two types of printing that continuous and drop on demand. But drop on demand process is becoming the mainstream. these days, LCD, PDP is passed more than semiconductor industry. And we expect organic EL, FED as a next display. But product equipment, main component and technology have a gap between an advanced country and us nevertheless physical development. Expecially, previous process part is depended on imports. Ink-jet printing technology that there isn't complicated photo lithography process is attracted, so ink-jet printing resolution is more embossed. But there were not many of ink-jet resolution thesis but ink-jet head or nozzle. Because, to out of the ink from the nozzle is unseeable and hard to experiment. Therefore this thesis was experimented and simulated how can ink-jet printer improved resolution by flow-3d simulation package program.

• International journal of advanced smart convergence
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• 제6권1호
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• pp.50-56
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• 2017

Wireless sensor nodes have limited energy, so it is important to optimize energy consumption to preserve network lifetime. Various protocols have been proposed for this purpose. LEACH protocol and SEP are the representative protocols. These protocols become less effective as the Sensor Field becomes wider. To improve this, MR-SEP and L-SEP were proposed. These protocols increase the energy efficiency by dividing the Sensor Field into layers and reducing the transmission distance. However, when dividing a layer, there are cases where it is divided inefficiently, and a node within a certain range from a Base Station has a better transmission efficiency than a direct transmission method using a cluster method. In this paper, we propose a Single-hop layer for L-SEP to improve inefficient layer division and near node transmission efficiency. When the larger the Sensor Field, the better the performance of the proposed method by up to 87%. The larger the sensor field, the more efficient the proposed method is over the conventional method. That is, the proposed method is suitable for the wide Sensor Field.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.940-943
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• 2003

We report the fabrication and the characterization of white organic light-emitting devices consisting of a red-emitting layer of a new DCM derivative doped into 4,4'bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (${\alpha}-NPD$) and a blue-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi). The device structure is ITO/PEDOT:PSS/${\alpha}-NPD$ (50 nm)/${\alpha}-NPD$:DCM (5 nm, 0.2 %)/DPVBi (x)/Alq3 (40 nm)/LiF (0.5 nm)/Al. The electroluminescence (EL) spectra consist of two broad peaks around 470 nm and 580 nm with the spectral emission depending on the thickness of DPVBi. The device with the DPVBi thickness of about 20 nm show a white light-emission with the Commission Internationale d'Eclairage(CIE) chromaticity coordinates of (0.33, 0.36). The external quantum efficiency is 2.6% and luminous efficiency is 2.0 lm/W at a luminance of 100 $cd/m^{2}$. The maximum luminance is about 30,270 $cd/m^{2}$ at 13.9 V.

• 한국전기전자재료학회논문지
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• 제18권12호
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• pp.1139-1142
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• 2005

Recently, organic light emitting diodes(OLEDs) is widely used as one of the information display techniques. We synthesized 2-(2-hydroxyphenyl)benzoxazole($Zn(HPB)_2$). We studied the luminescent properties of OLEDs using $Zn(HPB)_2$. The ionization potential(IP) and the electron affinity(EA) of $Zn(HPB)_2$ investigated using cyclic-voltammetry(C-V). The IP and EA were 6.5 eV and 3.0 eV, respectively. The PL and EL spectra of $Zn(HPB)_2$ were observed at the wavelength of 450 nm. We used $Zn(HPB)_2$ as an emitting layer and hole blocking layer. At the experiment about hole blocking effect, we inserted $Zn(HPB)_2$ between emiting material layer(EML) and cathode, and between hole transport layer(HTL) and emitting material layer(EML). We measured current density-voltage and luminance-voltage characteristics at room temperature.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.841-846
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• 2011

New green host materials, 9-phenyl-3-(4-(1-phenyl-1H-benzo[d] imidazol-2-yl)phenyl)-9H-carbazole (3a) and 9-(naphthyl-2-yl)-3-(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)-9H-carbazole (3b), have been designed and synthesized by attaching the electron transporting benzimidazole moiety to the hole transporting carbazole unit. These compounds have similar HOMO, LUMO levels and band-gap characteristics compared with CBP (4,4'-di(N-carbazolyl)biphenyl). The fabricated green phosphorescent OLED with this 3a host shows much better device performances compared to CBP-based one. The current and power efficiency is enhanced at least by 60 percent at a given constant luminance of 1000 cd/$m^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.1014-1018
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• 2007

We have demonstrated the enhancement of the power efficiency and device lifetime of organic light-emitting diodes (OLEDs) by introducing the ETL 1 / ETL2 (composite ETL) structure between EML and cathode and the HIL1 (composite HIL) / HIL2 between anode and HTL. Compared to reference devices retaining conventional architecture, novel OLED structure shows an outstanding EL efficiency that is 1.6 times higher (${\sim}4.5$ lm/w versus ${\sim}$ 2.71 lm/w for the reference device) and lower driving voltage $({\bigtriangleup}V>1V)$, but also a longer lifetime and smaller operating voltage drift over time. It is suggested in this work that the device performance can be improved by in-situ ohmic contact through novel electron controlled structure and reduction of charge accumulation in the interface through composite HIL