• 한국응용과학기술학회지
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• 제21권4호
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• pp.274-278
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• 2004

In this study, hetero-electrode structures have been fabricated to increase luminescence efficiency. The presence of a thin layer of Sn or Ag at the organic-aluminum interface enhanced both electron injection efficiency and electroluminescence when compared to OLEDs using homogeneous electrode. In this paper, the effect of the cathode using Sn/Al hetero electrode structure is observed. Electric properties of the OLED using Sn/Al hetero cathode are improved in comparison of only Al cathode. The hetero-electrode existing different energy level induces the advanced structure of OLED can accumulate electron density. The luminescence efficiency of OLED with Sn/Al of Ag/Al cathode is higher because of their higher electron injection efficiency. And, the turn on voltage of the OLED device using Sn thin layer is lowest as about 10 V.

• Preventive Nutrition and Food Science
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• 제6권4호
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• pp.216-223
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• 2001

A study was carried out to examine the effect of sample form and storage conditions on the accumulated PPSL signals. Korean perilla and sesame seeds were tested as whole samples and separated minerals. Radiation-induced PPSL signals of perilla and sesame seeds themselves significantly increased with irradiation dose up to 5 kGy. On the other hand, a slight decrease in the accumulated PPSL signals was shown at 10 kGy. Similar results were also found in separated minerals. The accumulated PPSL signals of irradiated samples decreased with increasing storage periods. The decay rate was higher in 5 or 10 kGy-irradiated samples than in 1 kGy, in room conditions than in darkroom conditions, and in sesame and perilla seeds themselves than in separated minerals. The accumulated PPSL signals of the irradiated samples measured fur 120 s were higher than those measured for 60 s. These results indicated that although the PPSL signal of all samples decreased with increasing the storage time, detection of irradiated samples was still possible after 12 months of storage regardless of sample form and measurement times (60 and 120 s) in both room and darkroom conditions.

• 한국세라믹학회지
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• 제35권2호
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• pp.145-150
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• 1998

ZnGa2O4 thin film phosphors were deposited on Si(100) (111) wafers by rf magnetron sputtering. The ef-fects of substrates and deposition parameters on the growing mechanisms were studied. As a results of the effect of substrate temperature tranistions of growth orientation and different growing behaviors were ob-served. Also polycrystalline ZnGa2O4 thin film could not be achieved without oxygen gas. PL spectrum of ZnGa2O4 thin films were analyzed and showed broad band luminescence spectrum.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.239-242
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• 2002

Luminescence efficiency of phosphors, $SrTiO_3;Pr^{3+}$ and $SrIn_2O_4:Pr^{3+}$, is increased remarkably by III-group impurities. This effect is explained by a picture that carriers thermally released from impurity-induced traps supply energy to $Pr^{3+}$ ions. The impurities also improve carrier transport efficiency by reducing lattice defects. This picture indicates a possibility to develop new ternary oxide phosphors.

• E2M - 전기 전자와 첨단 소재
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• 제17권7호
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• pp.21-29
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• 2004

절연성 기판 위에 단결정이 아닌 반도체 박막을 이용하여 만든 전계효과 (Field Effect FET) 소자로 일반적으로 정의되는 박막 트랜지스터 (Thin Film Transistor, TFT)는 1962 RCA lab.의 Weimer에 제안되어 지금까지 많은 발전을 거듭해 왔다. ［1］ TFT는 SRAM이나 ROM에도 응용되지만, 주된 사용 분야는 능동구동방식 평판 디스플레이(Active Matrix Flat Panel Display)의 화소 스위칭 소자이다. 액정 디스플레이(Liquid Crystal Display, LCD)나 유기 전계발광 디스플레이(Organic Electro-luminescence Display, OELD) 화소의 스위칭 소자로도 TFT가 널리 사용되고 있다. (중략)

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.267-270
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• 2013

• Korean Chemical Engineering Research
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• 제53권5호
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• pp.620-626
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• 2015

$Ho^{3+}$가 도핑된 $SrAl_2O_4$ 상향전환 형광체 분말을 분무열분해법으로 제조하고 활성제의 농도, 후 열처리 온도 변화에 따른 결정학적 구조와 발광 특성을 조사하였다. 또한 유기 첨가제 사용에 따른 형광체의 결정구조, 표면적 및 휘도 변화를 조사하였다. $SrAl_2O_4:Ho^{3+}$는 $Ho^{3+}$의 $^5F_4/^5S_2{\rightarrow}^5I_8$ 전이에 기인한 강한 녹색 발광을 보였다. 가장 높은 발광 강도를 보이는 $Ho^{3+}$ 농도는 0.1%였고, 그 이상의 농도에서는 활성 이온간 쌍극자-쌍극자 상호 작용에 의에 농도소강이 일어나 발광 휘도는 급격히 감소하였다. 여기 광원의 전력 세기에 따른 발광 휘도 변화 관찰로부터 $SrAl_2O_4:Ho^{3+}$의 녹색 발광은 2광자가 관여된 바닥상태흡수-여기상태흡수 과정을 통해 효율적으로 일어남이 확인되었다. 합성된 분말의 주상은 단사정계이고 일부 육방정계 상이 존재하였다. 후 열처리 온도를 $1000^{\circ}C$에서 $1350^{\circ}C$로 증가시킴에 따라 $SrAl_2O_4:Ho^{3+}$는 육방정계 상이 줄어 들면서 단상정계의 결정성이 향상되었다. 그러나 $1350^{\circ}C$에서도 일부 육방정계 상은 존재하였다. 구연산(CA)과 에틸렌 글리콜(EG)을 첨가해준 분무 용액으로부터 제조한 경우, 육방정계 상이 없는 순수한 단사정계 상으로 향상된 결정성을 가지는 $SrAl_2O_4:Ho^{3+}$가 제조되었다. 또한 유기 첨가제와 함께 N,N-Dimethylformamide(DMF)를 분무용액에 넣어 줌으로써 형광체의 표면적을 크게 감소시킬 수 있었다. 그 결과 CA/EG/DMF를 넣고 제조한 $SrAl_2O_4:Ho^{3+}$ 형광체는 유기 첨가물 없이 제조한 형광체에 비해 발광 휘도가 약 168% 향상되었다. 이러한 휘도 증대는 $SrAl_2O_4:Ho^{3+}$ 형광체의 결정상이 순수해졌고, 결정성 증대와 표면 결함을 최소화시킨 결과라고 결론지었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.280.1-280.1
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• 2016

Generally InGaN/GaN green light emitting diode (LED) exhibits the low quantum efficiency (QE) due to the large lattice mismatch between InGaN and GaN. The QE of InGaN-based multiple quantum wells (MQWs) is drastically decreased when an emission wavelength shifts from blue to green wavelength, so called "green gap". The "green gap" has been explained by quantum confined Stark effect (QCSE) caused by a large lattice mismatch. In order to improve the QE of green LED, undoped graded short-period InGaN/GaN superlattice (GSL) and Si-doped GSL (SiGSL) structures below the 5-period InGaN/GaN MQWs were grown on the patterned sapphire substrates. The luminescence properties of InGaN/GaN green LEDs have been investigated by using photoluminescence (PL) and time-resolved PL (TRPL) measurements. The PL intensity of SiGSL sample measured at 10 K shows stronger about 1.3 times compared to that of undoped GSL sample, and the PL peak wavelength at 10 K appears at 532 and 525 nm for SiGSL and undoped GSL, respectively. Furthermore, the PL decay of SiGSL measured at 10 K becomes faster than that of undoped GSL. The faster decay for SiGSL is attributed to the increased wavefunction overlap between electron and hole due to the screening of piezoelectric field by doped carriers. These PL and TRPL results indicate that the QE of InGaN/GaN green LED with GSL structure can be improved by Si-doping.

• 한국재료학회지
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• 제23권8호
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• pp.430-434
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• 2013

Quantum dots(QDs) with their tunable luminescence properties are uniquely suited for use as lumophores in light emitting device. We investigate the microstructural effect on the electroluminescence(EL). Here we report the use of inorganic semiconductors as robust charge transport layers, and demonstrate devices with light emission. We chose mechanically smooth and compositionally amorphous films to prevent electrical shorts. We grew semiconducting oxide films with low free-carrier concentrations to minimize quenching of the QD EL. The hole transport layer(HTL) and electron transport layer(ETL) were chosen to have carrier concentrations and energy-band offsets similar to the QDs so that electron and hole injection into the QD layer was balanced. For the ETL and the HTL, we selected a 40-nm-thick $ZnSnO_x$ with a resistivity of $10{\Omega}{\cdot}cm$, which show bright and uniform emission at a 10 V applied bias. Light emitting uniformity was improved by reducing the rpm of QD spin coating.At a QD concentration of 15.0 mg/mL, we observed bright and uniform electroluminescence at a 12 V applied bias. The significant decrease in QD luminescence can be attributed to the non-uniform QD layers. This suggests that we should control the interface between QD layers and charge transport layers to improve the electroluminescence.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1553-1558
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• 2009

A series of Eu(III) complexes with various neutral ligands (2,2’:6’,2"-terpyridine (T), diglyme (D), 1N-(2-dimethylamino) ethyl)-1N, 2N, 2N-trimethylethane-1,2-diamine (PT), di-(2-picolyl)-amine derivative (HT), and multidentate terpyridine derivative (DT)) were synthesized to investigate the effect of coordination environment on the sensitized luminescence of Eu(III) complexes. The nine coordination sites of the $Eu^{3+}$ ion are occupied by three bidentate carboxylate moieties and one neutral ligand. The highest emission intensity is obtained for $Eu^{3+}$- $[NA]_3$ (PT), due to the difference in energy transfer efficiency and symmetry of the first coordination sphere of $Eu^{3+}$ ion. But, the lowest emission intensity is obtained for $Eu^{3+}$-$[NA]_3$(T). Terpyridine may not play an important role antenna for photosensitizing $Eu^{3+}$ ion. It could be attributed to the weak spectral overlap integral J value between its phosphorescence band and $Eu^{3+}$ion absorption band. Therefore, different coordination environment of $Ln^{3+}$ ion play an important role in providing sensitization of lanthanide ion emission.