• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.56-59
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• 2009

In the nineties the invention of the InGaN blue LED has innovated illumination technology. Currently LCD backlighting and more and more general lighting applications are based on white LEDs comprising of inorganic phosphors and blue emitting InGaN chip. Well established phosphor materials are ortho silicates and garnets like yellow emitting YAG:Ce. In our paper we demonstrate that garnet materials also allow for green light emission for both, general lighting and backlighting LED applications.

• 한국세라믹학회지
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• 제53권2호
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• pp.253-257
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• 2016

We added 0 ~ 5 wt% $YBO_3:Eu^{3+}$ nano powders in a scattering layer of a working electrode to improve the energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC). FESEM and XRD were used to characterize the microstructure and phase. PL and micro Raman were used to determine the fluorescence and the composition of $YBO_3:Eu^{3+}$ phosphor. A solar simulator and a potentiostat were used to confirm the photovoltaic properties of the DSSC with $YBO_3:Eu^{3+}$. From the results of the microstructure and phase of the fabricated $YBO_3:Eu^{3+}$ nano powders, we identified $YBO_3:Eu^{3+}$ having particle size less than 100 nm. Based on the microstructure and micro Raman results, we confirmed the existence of $YBO_3:Eu^{3+}$ in the scattering layer and found that it was dispersed uniformly. Through photovoltaic properties results, the maximum ECE was shown to be 5.20%, which can be compared to the value of 5.00% without $YBO_3:Eu^{3+}$. As these results are derived from conversion of light in the UV range into visible light by employing $YBO_3:Eu^{3+}$ in the scattering layer, these indicate that the ECE of a DSSC can be enhanced by employing an appropriate amount of $YBO_3:Eu^{3+}$.

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.306-309
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• 2007

PXLM(Phosphor based x-ray light modulator) has a combined structure by phosphor, photoconductor, and liquid crystal and it can realize x-ray image of high resolution in clinical diagnosis area. In this study, we fabricated a photoconductor and investigated electrical and optical properties to confirm application possibility of radiator detector of PXLM structure. As photoconductor, amorphous selenium(a-Se), which is used most in DR(Digital radiography) of direct conversion method, was used and for formation of thin film, it was formed as $20{\mu}m-thick$ by using thermal vacuum evaporation system. For a produced a-Se film, through XRD(X-ray diffraction) and SEM(Scanning electron microscope), we investigated that amorphous structure was uniformly established and through optical measurement, for visible light of 40 $0\sim630nm$, it had absorption efficiency of 95 % and more. After fabricated a-Se film on the top of ITP substrate, hybrid structure was manufactured through forming $Gd_2O_3:Eu$ phosphor of $270{\mu}m-thick$ on the bottom of the substrate. As the result to confirm electrical property of the manufactured hybrid structure, in the case of appling $10V/{\mu}m$, leakage current of $2.5nA/cm^2$ and x-ray sensitivity of $7.31nC/cm^2/mR$ were investigated. Finally, we manufactured PXLM structure combined with hybrid structure and liquid crystal cell of TN(Twisted nematic) mode and then, investigated T-V(Transmission vs. voltage) curve of external light source for induced x-ray energy. PXLM structure showed a similar optical response with T-V curve that common TN mode liquid crystal cell showed according to electric field increase and in appling $50\sim100V$, it showed linear transmission efficiency of $12\sim18%$. This result suggested an application possibility of PXLM structure as radiation detector.

• 전자공학회논문지
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• 제51권12호
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• pp.189-194
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• 2014

본 연구에서는 새로운 구조의 X선 영상 검출기로써 광민감 $HgI_2$ 층이 포함된 CsI:Na 형광층의 구조를 설계하였다. 이러한 구조에서 X선은 두꺼운 CsI:Na 층에서 가시광선으로 변환된 후 하부의 얇은 $HgI_2$ 층에서 전하로 변환된다. CsI:Na와 $HgI_2$로 구성된 복합구조의 두께를 최적화하기 각 층의 두께를 변화시켜 X선에 대한 흡수효율을 시뮬레이션 하였다. 현재 상용화된 a-Se 단일층의 검출기는 수십 kV의 고전압이 요구되고, CsI:Na/a-Si 구조의 간접변환 방식은 낮은 변환효율을 가지는 단점이 있다. 본 연구의 결과로 제시된 새로운 형태의 CsI:Na/$HgI_2$ 복층 구조의 x-ray 검출기는 고전압이 필요한 직접 변환방식의 단점과 간접 변환방식의 낮은 효율을 보완할 수 있을 것으로 생각된다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.49-49
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• 2009

Phosphors with oxide host material, YAG:$Ce^{3+}$ and $(Ca,Sr,Ba)_2SiO_4:Eu^{2+}$ yellow phosphor, has been used for LED applications. The WLEDs using these phosphors are widely used for LCD backlighting, automobile, and general lighting applications since they have high conversion efficiency and good thermal and chemical stability which can meet necessary life time of LED products up to now. With advances of LED chip technology, the external quantum efficiency and driving current in chip get higher so that the phosphors for high power chip are required to maintain high conversion efficiency and stability at high temperature due to the heat dissipated from LED chips. In addition, higher color rendering index of LED lighting and color reproducibility of LCD than those of LEDs with single yellow phosphors are required. In order to overcome these technical issues rising from evolution of LED technology, new phosphors are in demand and nitride phosphors, one of the promising new candidate materials, will be discussed here.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.223-227
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• 2003

In this study, ultrasonic rotary motors using a bolted langevin type ultrasonic vibrator were designed and fabricated. The stator vibrator has a longitudinal transducer section composed of two metal blocks and two piezoelectric ceramic elements (thickness-polarized) and a mode conversion metal block section called a torsion coupler. And, three kinds of motors were studied by finite element analysis and experiments. So, as material of torsion coupler which generate mode conversion of vibration copper, brass, and phosphor bronze were used. As a result, speed and torque were changed in proportion to the electrical input Voltage, but it was saturated in high voltage. And bad efficiency which was different from a expectation was measured in this motors. So, various problems should be improved for practical use. Finally, The motor which has 1 [cm] diameter was fabricated to present a possibility of miniaturization of this type motors.

• 생물환경조절학회지
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• 제25권2호
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• pp.111-117
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• 2016

본 연구의 목적은 광전환재의 사이즈가 다른 광전환 필름을 피복한 온실에서, 실내 생육 환경, 토마토 및 상추의 생육과 품질을 분석하는 것이다. $10{\mu}m$ 이상의 광전환재를 이용한 광전환 필름(Micro 필름), 500nm 이하의 광전환재를 이용한 광전환 필름(Nano 필름)과 폴리에틸렌(PE) 필름을 2중 온실의 외피복재로 피복하였다. 내피복재는 0.06mm PE 필름을 사용하였고, 내피복재 및 외피복재의 두께는 모두 0.06mm로 동일하였다. 광전환 필름의 인장강도, 인열강도, 신장율은 PE 필름과 유사하였다. 투광률은 Nano 필름이 600-750nm 및 전체 투광률에서 PE 필름보다 높았으며, Micro 필름은 PE 필름보다 전체 투광률이 낮았다. 온실 내 기온은 Micro 및 Nano 필름 온실이 PE 필름 온실에 비하여 약 $2^{\circ}C$정도 높았고, 광전환 필름 온실 간의 유의적인 차이는 없었다. 지온은 Nano 필름 온실이 Micro 필름과 PE 온실에 비하여 각각 1.5, 3 정도 높았다. 토마토의 수량은 PE 필름 온실에 비해 Micro 및 Nano 필름 온실에서 각각 12%, 14% 정도 유의적으로 증가하였고, 당도 차이는 없었다. 그리고 광전환 필름 간의 유의적인 차이는 없었다. 상추의 수량은 Micro 필름 온실이 Nano 필름 및 PE 필름 온실에 비하여 각각 27%, 59% 높았다. Hunter의 적색 값 a는 Nano 필름 온실에서 가장 높았다. 토마토와 같이 높은 광을 요구하는 작물은 투광률이 좋은 Nano 필름이 적합하였고, 상추와 같이 낮은 광을 요구하는 작물은 상추는 Micro 필름이 적합하다고 판단되었다.

• Korean Chemical Engineering Research
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• 제49권3호
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• pp.320-324
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• 2011

TOPO/TOP로 안정화된 CdSe 반도체 발광 나노입자를 용해열 방법을 이용하여 합성하였다. 합성 온도 및 시간 조절을 통하여 540 nm 녹색 발광과 620 nm 적색발광 CdSe 나노입자를 얻었다. 형광체 변환 백색 발광다이오드(LED)는 460 nm 발광 InGaN 발광다이오드(LED) 여기원(excitation)과 540, 620 nm 발광 CdSe 나노입자 형광체를 결합하여 제작하였다. CdSe 나노입자 형광층은 녹색과 적색이 혼합된 단층과 분리된 다층구조로 이루어졌으며, 형광층 구성에 따른 백색 LED 소자의 특성 차이를 비교하였다. 단층구조 백색 LED는 20 mA에서 5.78 lm/W의 효율을 가지며, 형광층 내에서의 에너지 전이로 인하여 적색광이 강한(0.36, 0.45)의 색좌표를 보였다. 반면 다층 구조 백색광 LED는 20 mA에서 7.28 lm/W의 효율과 순수 백색광 영역인(0.32, 0.34)의 색좌표를 나타냈다. 또한, 400 nm의 청자색 LED를 여기원으로 적용 시, 소자의 효율이 8.76 lm/W로 증가하였다.

• Imaging Science in Dentistry
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• 제40권4호
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• pp.155-158
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• 2010

Digital radiographic systems allow the implementation of a fully digital picture archiving and communication system (PACS), and provide the greater dynamic range of digital detectors with possible reduction of X-ray exposure to the patient. This article reviewed the basic physical principles of digital radiographic imaging system in dental clinics generally. Digital radiography can be divided into computed radiography (CR) and direct radiography (DR). CR systems acquire digital images using phosphor storage plates (PSP) with a separate image readout process. On the other hand, DR systems convert X-rays into electrical charges by means of a direct readout process. DR systems can be further divided into direct and indirect conversion systems depending on the type of X-ray conversion. While a direct conversion requires a photoconductor that converts X-ray photons into electrical charges directly, in an indirect conversion, lightsensitive sensors such as CCD or a flat-panel detector convert visible light, proportional to the incident X-ray energy by a scintillator, into electrical charges. Indirect conversion sensors using CCD or CMOS without lens-coupling are used in intraoral radiography. CR system using PSP is mainly used in extraoral radiographic system and a linear array CCD or CR sensors, in panoramic system. Currently, the digital radiographic system is an important subject in the dental field. Most studies reported that no significant difference in diagnostic performance was found between the digital and conventional systems. To accept advances in technology and utilize benefits provided by the systems, the continuous feedback between doctors and manufacturers is essential.

• 한국방사선학회논문지
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• 제3권4호
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• pp.35-38
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• 2009

최근 의료영상분야에서 형광체와 광도전체 물질을 이용한 디지털 평판형 X선 영상검출기가 폭넓게 이용되고 있다. 본 연구는 CsI:Na 형광체층과 광민감도가 우수한 비정질 셀레늄(a-Se)층의 이중 접합구조로 구성된 변환구조 설계를 위한 몬테카를로 시뮬레이션과 X선에 대한 광학적 및 전기적 반응특성을 조사하였다. 먼저 CsI:Na의 발광스펙트럼과 a-Se의 광흡수 스펙트럼을 측정하여 X선에 의한 신호 변환특성을 분석하였다. 또한, 인가전기장의 함수에 따른 X선 민감도을 측정하여 상용화된 a-Se($500{\mu}m$)의 직접변환 검출기와 비교 평가하였다. 측정결과로부터, $10V/{\mu}m$에서 CsI:Na($180{\mu}m$)/a-Se($30{\mu}m$) 변환센서의 X선 민감도는 $7.31nC/mR-cm^2$ 이고, a-Se($500{\mu}m$) 검출기는 $3.95nC/mR-cm^2$로 약 2배 정도 높은 값을 보였다.