• 대한방사선기술학회지:방사선기술과학
• /
• 제16권1호
• /
• pp.41-55
• /
• 1993

Recently, various screen film system have been introduced in diagnostic radiology. There are two kinds of screen film system : blue emitting $CaWO_4$ screen has been largely used in these days. However, it tends to be changed to use green emitting $Gd_2O_2S$ : Tb screen. In this study, photographic characteristics of $CaWO_4$ and $Gd_2O_2S$ : Tb screen were investigated with luminescence, spectroscopy. The morphology of $CaWO_4$ and $Gd_2O_2S$ : Tb were also observed by using scanning electron microscope. The result obtained were as follows : 1. There was small difference in the thickness of phosphor layers for the front and back screen of blue emitting system, but little difference in those of green emitting system. 2. There was no difference in the size of phosphor particles between the front and back screen for each screen. However, the particle size was different for the various kinds of screens. 3. The shape of phosphor particle was round with many faces for all the screens. 4. In the exposure of X-ray with the same intensity, luminescent intensity of a green emitting system was $6{\sim}7$ times larger than that of a blue emitting system. 5. The thickness of phosphor layers does not affect on the sensitivity of the screens exposed by X-ray.

• 한국전기전자재료학회논문지
• /
• 제26권6호
• /
• pp.451-456
• /
• 2013

To study emission properties of white phosphorescent organic light emitting devices (PHOLEDs), we fabricated white PHOLEDs of ITO(150 nm) / NPB(30 nm) / TcTa(10 nm) / mCP(7.5 nm) / light-emitting layer(25 nm) / UGH3(5 nm) / Bphen(50 nm) / LiF(0.5 nm) / Al(200 nm) structure. The total thickness of light-emitting layer with co-doping and blue-doping/co-doping using a host-dopant system was 25 nm and the dopant of blue and red was FIrpic and $Bt_2Ir$(acac) in UGH3 as host, respectively. The OLED characteristics were changed with position and thickness of blue doping layer and co-doping layer as light-emitting layer and the best performance seemed in structure of blue-doping(5 nm)/co-doping(20 nm) layer. The white PHOLEDs showed the maximum current density of $34.5mA/cm^2$, maximum brightness of $5,731cd/m^2$, maximum current efficiency of 34.8 cd/A, maximum power efficiency of 21.6 lm/W, maximum quantum efficiency of 15.6%, and a Commission International de L'Eclairage (CIE) coordinate of (0.367, 0.436) at $1,000cd/m^2$.

• 한국실내디자인학회논문집
• /
• 제23권5호
• /
• pp.25-32
• /
• 2014

The purpose of this study is to analyze the expression method and visual characteristics of material utilized the lighting in terms of a visual aspect. The method of study is to establish standards for analysis and to classify type of visual effect and expression of that focused on preliminary study. And It is to grasp the visual expression characteristics of new materials. through analysis standards. The results of the study are as follows. First, 'decorativeness', 'symbolization', 'motion-images' and 'interactivity' were selected as the type of visual expression through the precedent studies. And it was classified the visual effects as 3 types like 'a light-emitting effect', 'steric effects' and 'movement effect'. Second, We could know that 'light-emitting effect' was expressed in 7-new materials, 'three-dimensional effect' was expressed in 3-new materials, and 'motion effect' in 4-new materials. Through that. We could know that the new materials represented with 'light-emitting effect' are much more than the other new materials. Third, the results of this study show that 'decorativeness' in the visual types was appeared to 'light-emitting effect' and 'three-dimensional effect'. 'symbolization' to 'light-emitting effect' and 'motion effect', 'motion-images' to 'three-dimensional effect' and 'motion effect' and 'interactivity' to 'light-emitting effect', 'three-dimensional effect' and 'motion effect'. And It was appeared to three effects in 'interactivity'. We could know that it is more effective to be presented the visual effect simultaneously to communication with the visual perception.

• 생물환경조절학회지
• /
• 제9권4호
• /
• pp.223-229
• /
• 2000

식물묘의 생장 및 형태형성 제어용 인공광원으로서 조합광 LED 모듈을 제작하여 조합광 LED모듈의 광전기 특성을 분석하고, 광량자 센서와 분광광도계를 이용하여 LED 모듈로부터 조사된 광량자속에 대한 정량화를 시도하였다. 청색과 적생의 단색광 LED로부터 조사된 광량자속을 광량자센서로 측정한 값과 분광광도계로 측정하여 수치적으로 적분한 값을 qly한 결과 거의 일치하는 것으로 나타났다. 이러한 결과는 광량자센서로서 측정이 불가능한 원적색광 LED로부터의 광량자속 정량화에 분광광도계를 적용될 수 있음을 의미하는 것이다. 적생광에 원적색광을 조사하는 LED스틱의 혼합 비율을 달리한 조합광 LED 모듈의 광량지속은 원적색광을 조사하는 LED 스틱이 증가할수록 조합광 LED의 광량자속이 조금씩 증가하였다. 이러한 결과는 단위에너지당 조사된 광량지수는 파장에 비례해서 증가히기 때문인 것으로 해석된다. 이밖에 적색과 원적색광 LED 스틱의 조합 비율을 달리하였을 때 조합광 LED 모듈의 조도는 비시감도가 매우 낮은 원적색광이 차지하는 비율이 클수록 낮게 나타났다. 한편 적색광과 원적생광의 혼합 정도가 조합광 LED의 복사조도에 미치는 영향은 거의 없는 것으로 나타났다.

• 한국전기전자재료학회논문지
• /
• 제19권4호
• /
• pp.379-385
• /
• 2006

A stacked white organic light-emitting diode (OLED) having a blue/orange emitting layer was fabricated by synthesizing nitro-DPVT, a new derivative of the blue-emitting material DPVBi on the market. The white-emission of the two-wavelength type was successfully obtained by using both nitro-DPVT for blue~emitting material, orange emission as a host material and Rubrene for orange emission as a guest material. The basic structure of the fabricated white OLED is glass/ITO/NPB$(200{\AA})$/nitro-DPVT$(100{\AA})$/nitro-DPVT:$Rubrene(100{\AA})/BCP(70{\AA})/Alq_3(150{\AA})/Al(600{\AA})$. To evaluate the. characteristics of the devices, firstly, we varied the doping concentrations of fluorescent dye Rubrene from 0.5 % to 0.8 % to 1.3 % to 1.5 % to 3.0 % by weight. A nearly pure white-emission was obtained in CIE coordinates of (0.3259, 0.3395) when the doping concentration of Rubrene was 1.3 % at an applied voltage of 18 V. Secondly, we varied the thickness of the NPB layer from $150{\AA}\;to\;200{\AA}\;to\;250{\AA}\;to\;300{\AA}$ by fixing doping with of Rubrene at 1.3 %. A nearly pure white-emission was also obtained in CIE coordinates of (0.3304, 0.3473) when the NPB layer was $250-{\AA}$ thick at an applied voltage of 16 V. The two devices started to operate at 4 V and to emit light at 4.5 V. The external quantum efficiency was above 0.4 % when almost all of the current was injected.

• 한국콘텐츠학회논문지
• /
• 제8권11호
• /
• pp.18-24
• /
• 2008

유기 발광 다이오드(Organic light-emitting diode, OLED)는 저전력 구동, 자체발광, 넓은 시야각, 우수한 고해상도, 풀 칼라, 높은 재현성, 빠른 응답속도, 간편한 제조 공정 등의 장점을 가지고 있으나, 고성능 디스플레이로서 실용화하기 위해서는 아직도 해결되어야 할 과제가 많다. 소자의 저소비전력, 제조공정의 안정성, 대형 기판기술, 봉지 기술, 소자의 수명, 풀 컬러화를 위한 적색, 청색, 발광 소자의 고휘도등이 시급하다. 무엇보다 중요한 것은 유기 발광 소자의 효율을 향상시키는 것이 상용화를 위한 키(key)이다. 이를 위해서 유기 발광 소자의 구조 개선과 새로운 유기 물질 적용을 통해 구동전압을 낮춤으로써 효율을 향상시킬 수 있다. 따라서 본 연구에서는 유기 발광 소자의 효율을 향상시킬 목적으로 ITO/TPD/Znq2+DCJTB/Znq2/Al의 구조와 ITO/CuPc/NPB/Alq3+DCJTB/Alq3/Al의 구조를 가지는소자의 발광 층에 형광염료를 도포한 적색 발광 소자를 제작하고, 그 전기적 및 광학적인 특성을 평가하였다.

• Current Optics and Photonics
• /
• 제1권4호
• /
• pp.389-395
• /
• 2017

This paper investigates a method to improve the lighting performance of white light-emitting diodes (WLEDs), which are packaged using two separate remote phosphor layers, a yellow-emitting YAG:Ce phosphor layer and a red-emitting ${\alpha}-SrO{\cdot}3B_2O_3:Sm^{2+}$ phosphor layer. The thicknesses of these two layers are $800{\mu}m$ and $200{\mu}m$, respectively. Both of them are examined in conditions where the average correlated color temperatures (CCT) are 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor is varied from 2% to 30% in the upper layer, while in the lower layer the yellow phosphor concentration is kept at 15%. It was found interestingly that the lighting properties such as color rendering index (CRI) and luminous flux are enhanced significantly, while the color uniformity is maintained in a relatively close range to the one of one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer are revised by combining Kubelka-Munk and Mie-Lorenz theories. Through analysis, it is demonstrated that the packaging configuration of two-layer remote phosphor that employs red-emitting ${\alpha}-SrO{\cdot}3B_2O_3:Sm^{2+}$ phosphor particles provides a practical solution for general WLEDs lighting.

• Transactions on Electrical and Electronic Materials
• /
• 제16권3호
• /
• pp.124-129
• /
• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• 한국콘텐츠학회:학술대회논문집
• /
• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
• /
• pp.301-305
• /
• 2008

유기 발광 다이오드(Organic light-emitting diode, OLED)는 저전력 구동, 자체발광, 넓은 시야각, 우수한 고해상도, 풀 칼라, 높은 재현성, 빠른 응답속도, 간편한 제조 공정 등의 장점을 가지고 있으나, 고성능 디스플레이로서 실용화하기 위해서는 아직도 해결되어야 할 과제가 많다. 소자의 저소비전력, 제조공정의 안정성, 대형 기판기술, 봉지 기술, 소자의 수명, 풀 컬러화를 위한 적색, 청색, 발광소자의 고휘도 등이 시급하다. 무엇보다 중요한 것은 유기 발광 소자의 효율을 향상시키는 것이 상용화를 위한 키(key) 이다. 이를 위해서 유기 발광 소자의 구조 개선과 새로운 유기 물질 적용을 통해 구동전압을 낮춤으로써 효율을 향상시킬 수 있다. 따라서 본 연구에서는 유기 발광 소자의 효율을 향상시킬 목적으로 ITO/TPD/Znq2+DCJTB/Znq2/Al의 구조와 ITO/CuPc/N PB/Alq3+DCJTB/Alq3/Al의 구조를 가지는 소자의 발광층에 형광염료를 도포한 적색 발광 소자를 제작하고, 그 전기적 및 광학적인 특성을 평가하였다.

• 한국전기전자재료학회논문지
• /
• 제25권11호
• /
• pp.910-915
• /
• 2012

We studied the emission characteristics of white phosphorescent organic light-emitting diodes (PHOLEDs), which were fabricated using a two-wavelength method. The best blue emitting OLED and red emitting OLED characteristics were obtained at a concentration of 12 vol.% FIrpic and 1 vol.% $Bt_2Ir$(acac) in UGH3, respectively. And the optimum thickness of the total emitting layer was 25 nm. To optimize emission characteristics of white PHOLEDs, white PHOLEDs with red/blue/red, blue/red, red/blue and co-doping emitting layer structures were fabricated using a host-dopant system. In case of white PHOLEDs with co-doping structure, the best efficiency was obtained at a structure UGH3: 12 vol. % FIrpic: 1 vol.% $Bt_2Ir$(acac) (25 nm). The maximum brightness, current efficiency, power efficiency, external quantum efficiency, and CIE (x, y) coordinate were 13,430 $cd/m^2$, 40.5 cd/A, 25.3 lm/W, 17 % and (0.49, 0.47) at 1,000 $cd/m^2$, respectively.