• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.69-72
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• 2014

White LEDs, based on blue LED chips coated with a yellow emitting phosphor (YAG:Ce), have several disadvantages. In this paper, we report the improvement in CRI [Color Rendition Index] using $GdAl_5O_{12}:Ce$ (GdAG:Ce) and related phosphors for blue LEDs. A modified combustion synthesis route using mixed fuel was used for synthesis route. By using this procedure, we formed the desired compounds in a single step. LEDs were then fabricated by coating the blue LED chips (CREE 470 nm, 300 micron) with the GdAG:Ce phosphor dispersed in epoxy resin. The CRI typically between 65~70 for the YAG:Ce based LED was improved to 87 for LEDs fabricated from the Gd(Al,Ga)G phosphors.

• Journal of Information Display
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• 제12권4호
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• pp.219-222
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• 2011

Iridium-(III)-bis[(4,6-di-fluorophenyl)-pyridinate-N,$C^2$' ]picolinate-based blue phosphorescent organic light-emitting diodes with different electron transport materials were fabricated. Each electron transport material had different electron mobilities and triplet energies. The device with 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene had the highest external quantum efficiency (20.1%) and luminous current efficiency (33.1 cd/A) due to its high electron mobility and triplet energy. The operational stability of each device was also compared with that of the others. The device with 2,2',2"(1,3,5-benzenetriyl)tris-(1-phenyl-1H-benzimidazole) was found to have a longer lifetime than the other devices.

• Bulletin of the Korean Chemical Society
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• 제22권11호
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• pp.1181-1182
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• 2001

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1433-1436
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• 2007

Using a blue emitting DPVBi material and red dopant DCJTB, WOLEDs with and without green emitter C6 added in ETL or HTL have been fabricated. The chromaticity color index of WOLEDs without C6 depends strongly on the doping concentration. In addition, manipulating thickness of emitting layer is similar effect such as controlling weight concentration of dopant. While the white color of WOLEDs with C6 added in ETL or HTL depend on position of C6. WOLED of three colors added green dye have been shown turn-on voltage of 3.25V, and EL efficiency 3.05cd/A @9V, $8102\;cd/m^2$, CIE coordinates (0.30, 0.32).

• 한국재료학회지
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• 제14권10호
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• pp.749-753
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• 2004

In this study, we attempt to synthesize the $Sr_{3}SiO_{5}:Eu$ yellow phosphor by sol-gel technique. Based on the blue emitting diodes as primary light source, white light emitting diodes have been manufactured using the $Sr_{3}SiO_{5}:Eu$ yellow phosphor as the luminescent material. Luminescent efficiency of yellow phosphor as well as that of blue LED is very important factor to enhance the luminescent efficiency of white LED. In order to improve the luminescent efficiency, we have synthesized the $Sr_{3}SiO_{5}:Eu$ phosphor by sol-gel technique. To research optimum condition of gelation reaction, the ratio of $H_{2}O$ to TEOS was fixed as 60:1. When the drying temperature was at $100^{\circ}C$, emission intensity was better than at $70^{\circ}C$. The critical $Eu^{2+}$ concentration was estimated to be about 0.05 mol and sintering temperature at $1300^{\circ}C$ was indicated best emission intensity.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 디스플레이 광소자분야
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• pp.43-46
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• 2004

We demonstrated efficient white light emitting OLEDs with a single emissive layer structure, which was blue-emitting 1,4-bis[2,2-diphenylvinyl]biphenyl (DPVBi) doped with blue luminescent amino-substituted distyrylarylene amine (DSA-amine) and red luminescent [2,6-bis[2-[5-(dibutylamino) phenyl]vinyl]-4H -pyran-4-ylidene]propanedinitrile (DADB). Through the optimization of the device structure, the white light emission with full visible spectral range was obtained. Its CIE color coordinates was (0.32,0.42) at 10 $mA/cm^2$ and the external quantum efficiency, the luminance efficiency and the luminance yield were 3.7 %, 3.3 lm/W and 9.0 cd/A, respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.997-999
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• 1999

We fabricated white light-emitting organic electroluminescent device which have a mixed single emitting layer containing poly(N-vinylcarbazole)[PVK], tris(8-hydroxyquinoline)aluminum[Alq3] and poly(3-hexylthiophene)[P3HT] and investigated the emission properties of it. We expect to obtain a blue light from PVK, green light from Alq3 and red light from P3HT The fabricated device emits white light over 18V with slight orange light. We think that the energy transfer in a mixed layer occurred from PVK to $Alq_3$ and P3HT resulted in decreasing the blue light intensity from PVK. With mixing of N, N'-diphenyl-N, N'-(3-methylphenyl)-[1,1'-biphenyl]-4, 4'-diamine[TPD], hole transport material, to the emitting layer, the luminance intensity of device was increased 50 times than that of the device which not contain TPD. We find that the efficiency of the white light electroluminescent device can be improved by injecting electron more effectively and blue light need to improve the color purity of white light.

• 한국응용과학기술학회지
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• 제39권5호
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• pp.589-595
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• 2022

안트라센의 골격을 갖는 청색 발광 물질, 9-(2-naphthyl)-10-(p-tolyl)anthracene (2-NTA)를 기본으로 하고, 오렌지 도판트인 루브렌을 다양한 부피비로 사용하여 백색 유기발광소자를 제작하였다. 그 결과 C.I.E. 좌표가 (0.32, 0.39)인 백색 유기발광소자를 얻었다. 다양한 부피비의 소자 중 루브렌을 1.5% 이하로 증착된 소자가 3% 이상으로 증착된 소자 보다 전기발광 효율이 높았다. 더욱이 2-NTA를 포함하는 백색 유기발광소자는 같은 조전하에서 2-NTA 만의 청색 유기발광소자 보다 낮은 턴온 전압을 갖는다. 결론적으로 2-NTA는 적은 양의 오렌지 도판트만으로 순수한 백색 유기발광소자를 구현할 수 있다.

• 한국전기전자재료학회논문지
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• 제17권2호
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• pp.217-222
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• 2004

The white-light-emitting organic LED(OLED) with two-wavelength was fabricated using the DPVBi of blue emitting material and a series of orange color fluorescent dye(Rubrene) by vacuum evaporation processes. The basic structure of white-light-emitting OLED was ITO/NPB(150$\AA$)/DPVBi/Rubrene/BCP(100$\AA$)/Alq$_3$(150$\AA$)/Al(600$\AA$). We analyzed the fabricated device through the changes of the DPVBi and Rubrene layer's thickness. We obtained the white-light-emitting OLED with white color light and the CIE coordinate of the device was (0.29, 0.33) at applied voltage of 13V when the thickness of DPVBi layer was 210$\AA$ and the thickness of Rubrene layer was 180$\AA$. At a current of 100㎃/$\textrm{cm}^2$, the quantum efficiency was 0.35％ and at a voltage of 20V, it was 0.405％.

• 한국전기전자재료학회논문지
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• 제32권6호
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• pp.444-447
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• 2019

It was proven that the light outputs of blue GaN-based light-emitting diodes (LEDs) was seriously influenced by the application of external stress. We have simulated the wave function overlap of an electron and hole, which are significantly reduced by the development of stress. Consequently, its internal quantum efficiency decreased from 67.0% to 37.5%. To experimentally investigate the effect of stress, we designed and prepared a special zig system. By applying external tensile stress to compensate for the compressive stress innately developed in Blue LEDs, it was found that the optical output was greatly enhanced from 83.1 mcd to 117.2 mcd at a current of 100 mA, an increase of approximately 41%. In contrast, when the compressive stress is developed more by external compressive stress, we observed that the light output power was reduced from 89.0 mcd to 80.7 mcd, a decrease of approximately 9.3%.