• 한국재료학회지
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• 제28권1호
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• pp.18-23
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• 2018

To study the impedance characteristics of a fluorescent OLED according to the device structure, we fabricated Device 1 using ITO / NPB / $Alq_3$ / Liq / Al, Device 2 using ITO / 2-TNATA / NPB / $Alq_3$ / Liq / Al, and Device 3 using ITO / 2-TNATA / NPB / SH-1:BD / $Alq_3$ / Liq / Al. The current density and luminance decreased with an increasing number of layers of the organic thin films in the order of Device 1, 2, 3, whereas the current efficiency increased. From the Cole-Cole plot at a driving voltage of 6 V, the maximum impedance values of Devices 1, 2, and 3 were respectively 51, 108, and $160{\Omega}$ just after device fabrication. An increase in the impedance maximum value is a phenomenon caused by the charge mobility and the resistance between interfaces. With the elapse of time after the device fabrication, the shape of the Cole-Cole plot changed to a form similar to 0 or a lower voltage due to the degradation of the device. As a result, we were able to see that an impedance change in an OLED reflects the characteristics of the degradation and the layer.

• 반도체디스플레이기술학회지
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• 제11권1호
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• pp.21-27
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• 2012

The optical diffuser for direct-lit LED backlight unit was prepared by using extrusion compounding followed by thermoforming process. Poly(methyl methacrylate) (PMMA) with superior optical characteristics and polycarbonate (PC) with good thermal property were used as base resins, and crosslinked polystyrene (PS) and PMMA beads as diffusing agents were incorporated into resin matrix to derive light scattering and diffusing action. In the compounded plate, the diffusing beads were observed to be dispersed uniformly and distinctly in the continuous phase. The inclusion of polymeric beads up to 3 wt% substantially enhanced the optical characteristics such as luminance, luminance uniformity, haze for the diffuser. Two different diffusers of PC and PMMA-based compound with various compositions were compared in terms of measured optical, thermal, and mechanical properties, which would be expected to be utilized for the industrial application of LED backlight unit.

• 한국전기전자재료학회논문지
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• 제27권2호
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• pp.104-109
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• 2014

To operate organic light emitting device (OLED) with alternating current (AC) power source without AC/DC(direct current) converter, we fabricated the fluorescent OLED and measured the emission characteristics with AC and DC. The OLED operated by AC showed higher maximum current efficiency of 8.2 cd/A and maximum power efficiency of 8.3 lm/W. But current efficiency and power efficiency of AC driven OLED showed worse than DC driven OLED at high voltage above 10 V. This result can be explained by the peak voltage of AC was $\sqrt{2}$ times than DC, In case of low driving voltage the emission characteristics were improved by the peak voltage of AC, but in case of high driving voltage the emission efficiencies were decreased by the roll off phenomena. Finally, serial OLED arrays using twelve OLEDs driven by AC 110 V showed average voltage of 9.17 V, voltage uniformity of 99.0%, average luminance of $1,175cd/m^2$, luminance uniformity of 94.4%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.600-603
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• 2000

Recently, Display devices have become important in the information-oriented society and flat display devices are greatly demanded. Liquid crystal display(LCD) represents one of the most promising devices for large size desk-top monitors, notebook PC and car navigation system. However LCD cannot give forth light itself and must have backlight system. The most popular backlighting system is composed of a lighting-guide plate and CCFL as a lighting source. The number of CCFL must increase up if the area of display is increased. So a new backlighting source with high luminance is needed for large LCDs. In this paper, we proposed a surface discharge FFL with the new electrode structure like the needle shaped electrode as the variation of cell structure to high luminance and low power consumption. In comparison with different electrode structure it has low discharge voltage and current and good optical characteristics. So it has better discharge characteristics than different surface discharge FFL and can be fungible for a backlight as a lighting source in LCDs.

• Journal of Information Display
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• 제9권1호
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• pp.26-32
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• 2008

The dependence of optical performances of collimating films such as prism films and pyramid films on the reflecting properties of reflection films were investigated by using a ray tracing technique. The angular distribution of the luminance and the on-axis luminance gain were obtained by using a simple backlight model composed of a reflection film, a virtual flat light source, and a collimating film. Three kinds of reflecting properties were used, which were a perfect Lambertian reflector, a perfect mirror reflector, and a reflector having both diffuse and specular properties. It was found that the on-axis luminance gain was the highest in the simulation where a mirror reflector was used, while the viewing angle was the widest where the Lambertian reflector was used. This result indicates that it is necessary to optimize the simulation condition such as the reflecting properties in order to predict the optical performances of collimating films accurately. Quantitative correlation between the optical characteristics of collimating films and the reflecting properties of reflection films can be used to improve simulation technique for the development and the optimization of collimating films for LCD backlight applications.

• 한국재료학회지
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• 제20권6호
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• pp.294-300
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• 2010

In this study, we fabricated a polymer light emitting diode (PLED) and investigated its electrical and optical characteristics in order to examine the effects of the PFO [poly(9,9-dioctylfluorene-2-7-diyl) end capped with N,N-bis(4-methylphenyl)-4-aniline] concentrations in the emission layer (EML). The PFO polymer was dissolved in toluene ranging from 0.2 to 1.2 wt%, and then spin-coated. To verify the influence of the TPBI [2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)]electron transport layer, TPBI small molecules were deposited by thermal evaporation. The current density, luminance, wavelength and current efficiency characteristics of the prepared PLED devices with and without TPBI layer at various PFO concentrations were measured and compared. The luminance and current efficiency of the PLED devices without TPBI layer were increased, from 117 to $553\;cd/m^2$ and from 0.015 to 0.110 cd/A, as the PFO concentration increased from 0.2 to 1.0 wt%. For the PLED devices with TPBI layer, the luminance and current efficiency were $1724\;cd/m^2$ and 0.501 cd/A at 1.0 wt% PFO concentration. The CIE color coordinators of the PLED device with TPBI layer at 1.0 wt% PFO concentration showed a more pure blue color compared with the one without TPBI, and the CIE values varied from (x, y) = (0.21, 0.23) to (x, y) = (0.16, 0.11).

• 조명전기설비학회논문지
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• 제24권1호
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• pp.45-55
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• 2010

최근 서울시에는 도시의 야간경관을 풍성하게 하고 랜드마크성을 부여하는 미디어 파사드 건축물의 수가 증가하고 있지만 무분별한 미디어 파사드의 적용은 오히려 도시이미지를 저해하는 등의 문제가 제기되고 있다. 특히, 미디어 파사드는 기존 건물외관의 장식이나 경관조명에 비하여 조명면적이 크기 때문에 심미적 고려와 도시환경의 건강성을 위해서 지나친 밝기의 규제가 필요하다. 따라서 미디어 파사드 건축물의 야간조명 특성을 분석하여 지역 기준에 맞게 적절히 설계되어 있는지에 대한 검토가 필요하다. 본 연구의 목적은 미디어 파사드 건축물의 표면휘도와 색온도 등의 조명물리량을 측정하여 옥외 야간조명환경을 분석하는 것이다. 현재 서울에 위치한 대표성을 가진 5개 미디어 파사드 건축물을 선정하여 해당건물이 위치한 반대편도로의 측정점에서 CS-100 기기와 ProMetric-1400 기기를 이용하여 측정하였다. 미디어 파사드 조명부분의 표면휘도를 분석한 결과, 5개 건물 중 3개 건물의 휘도차는 크지 않아 디자인이 잘 된 것으로 났으나 5개 건물 중 4개 건물에서 서울시 기준인 $25[cd/m^2]$를 초과하는 것으로 나타났다. 또한, 색온도를 분석한 결과 대부분 5,500[K]이상의 한색이 측정되어 서울시 도로조명 색온도 기준인 4,000~5,000[K]의 범위를 벗어나는 것으로 나타났다.

• 전자공학회논문지D
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• 제35D권2호
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• pp.52-59
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• 1998

The ZnS:Mn thin film electroluminescent(TFEL) devices fabricated by ALE system were investigated. Yellow-orange light emission was observed when the applied voltage exceeded 134 V and luminance increased sharply as the applied voltage increased. Luminance of 568 Cd/c $m^{2}$ was obtained under 1 KHz sinusoidal voltage wave application at the peak applied voltage of 230 V. The peak wavelength of the emissionwas 577 nm. The C-V, Q-V, $Q_{t}$ - $F_{p}$ , L- $Q_{cond}$, and V- $Q_{pol}$ have been measured under theapplication of the trapezoidal wave with its pulse width varying 0 to 75 .mu.sec. The phoshor and the insulator capacitance of the TFEL device under test were 24.3 nF/c $m^{2}$ and 9 nF/c $m^{2}$, respectively. It was observed that the threshold voltage changed from 137V to 100V as the pulse width varied from 0 to 75 .mu.sec. The L- $Q_{cond}$ characteristics showed that the light emission increased in proportion to the $Q_{cond}$. The luminance increased from 386 Cd/ $m^{2}$ to 607 Cd/ $m^{2}$ when the $Q^{+}$$_{cond}$ increased from 1.3 .mu.C/c $m^{2}$ to 2.3 .mu.C/c $m^{2}$. The V- $Q_{pol}$ characteristics showed that the V was inversely proportional to $Q_{pol}$./. th/ was inversely proportional to $Q_{pol}$./. pol/./.

• Transactions on Electrical and Electronic Materials
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• 제9권3호
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• pp.105-109
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• 2008

Electrical characteristics of organic light-emitting diodes were investigated by varying a hole-size in evaporation boat in the device structure of ITO/tris(8-hydroxyquinoline) aluminum$(Alq_3)$/Al. The device was manufactured using a thermal evaporation under a base pressure of $5{\times}10^{-6}$ Torr. The $Alq_3$ emitting organics were evaporated to be a thickness of 100 nm at a deposition rate of $1.5{\AA}/s$. A cylindrical-shaped evaporation boat was made out of stainless steel with a small size of hole on top of the boat. Several evaporation boats were made having a different hole size on top; 0.8 mm, 1.0 mm, 1.5 mm, and 3.0 mm. We found that when the hole size on top of the evaporation boat is 1.0 mm, the average roughness is rather smoother compared to the other ones. Also, luminance and external quantum efficiency are superior to the others. Compared to the ones from the devices made with the hole-size of 0.8 mm boat. The luminance and external quantum efficiency of the device made with the hole-size of 1.0 mm boat were improved by a factor of seventy and thirty three, respectively. Also operating voltage is reduced to 2 V.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.878-881
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• 2006

본 논문에서는 다양한 전극재료로부터 빛의 밝기와 저항을 측정하였고 분석하였다. 외부전극의 새로운 재료와 공정기술은 램프제작에서 개선된 특성을 위해서 매우 중요하다. 본 실험에서는 외부전극을 형성하기 위한 다른 세가지 타입은 구리와 알루미늄 테이핑, 은 접착, 니켈과 구리의 무전해 도금 방법들이다. 밝기측정에서 램프유리위에 외부전극을 위한 니켈과 금플레이팅 방법에 의한 휘도의 결과를 나타내었고 또한 다른 전극재료를 사용한 방법에 의한 결과들과 비교하였다. 니켈과 금플레이팅 공정의 측정된 저항값은 휘도의 개선된 결과에도 불구하고 다소 더 높은 저항값을 나타내었다. 그러나 니켈과 니켈/금 도금방법은 가장 좋은 결과를 나타내었고 사전 표면 식각에 따른 약간의 다른 휘도를 나타내었다.