• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.33-33
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• 2010

Electrical properties of organic light-emitting diodes (OLEDs) were simulated by S.co's program. The OLEDs have stable operating parameters, high luminance, and high efficiency in simulation. The AF stands for amorphous fluoropolymer in simulation, and it was used as a hole-injection layer. In the five structure of OLEDs, an AF layer is sandwiched between the hole-transport layer and the ITO layer to increase the external quantum efficiency. By considering organic light-emitting diodes using an optimal energy gap of AF, it could contribute to the improvement of the efficiency of the device in the simulation.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.921-924
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• 2008

We investigated new deep blue emitting materials including a novel side group such as CB-203. CB-203 shows relatively 40% increased PL quantum efficiency and higher Tg of $30^{\circ}C$ compared to MADN. It exhibits high External Quantum Efficiency (EQE) of 7.18% that is two times bigger than MADN's, which is the best efficiency in case of non-doped blue fluorescence OLED device to our knowledge. And deep blue emitting materials with a new core structure (CB-301) have been synthesized. CB-301 exhibit excellent blue fluorescence properties. Undoped OLED devices using CB-301 as blue emitters was found to deep blue CIE value (0.154, 0.078) and exhibit high luminance efficiencies of 2.01cd/A at $10\;mA/cm^2$.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.185-197
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• 1996

We have adopted the strain compensated PBH(planar buried heterostructure) - LD in which the MQW active layer consisted of 1.4% compressively strained GainAsP (E$_{g}$ = 0.905eV) wells and 0.7% tensile strained GaInAsP(E$_{g}$ = 1.107eV) barriers grown by metal organic vapor phase epitaxy (MOVPE). We hav einvestigated effects of number of wells and the structure of the separate confinement heterostructure (SCH) layer in the strain-compensated MQW-PBH-LD. The threshold current, the external quantum efficiency, the transparency current density J$_{o}$, and the gain constant .beta. have been evaluated for uncoated MQW-PBH-LD. As the number of wells increases, the internal quantum efficiency and the transparency current density decreases, whereas the gain contant increases. The small width of the SCH layer shows the large internal quantum efficiency. The small internal loss and the large gain constant have been obtained by inserting the large bandgap SCH layer.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.3979-3989
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• 2021

Several parametric effects on the magnetic collection have been evaluated considering dimension, strength of external magnetic field, injected velocity and particle concentration in the working fluid. Besides, accidental environments, expected in the containment of nuclear power plants, have also been addressed for the capture efficiency. The capture efficiency is especially enhanced with magnetic particle size and magnetic field strength through increased magnetic force; the non-magnetic coating thickness and fluid velocity hinder the magnetic collection. Based on the assessment, the magnetic withdrawal system can effectively capture magnetic particles even under accidental environments. Withdrawal of multifunctional magnetic particles or filtering of magnetic impurities can be effectively realized through the system.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.225-225
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• 2016

PHOLED devices which have the structure of ITO/HAT-CN(5nm)/NPB(50nm)/EML(47nm)/TPBi(10nm)/Alq3(20nm)/LiF(0.8nm)/Al(100nm) are fabricated to investigate the diffusion length of the triplet exciton by using double-quantum-well(DQE) EML structure. To fabricate DQW structures, Ir(ppy)3(2% wt) and Ir(btp)2(8% wt) are used as green and red emission zones, respectively. In DQW structured EML, as shown in Fig. 1, 1nm thick layers of green and red emission zones are located middle of the EML, and the distance between these wells(x) is changed from 0nm to 10nm. As shown in Fig. 2, the emission spectra from DQW PHOLED devices are changed with different x. The intensity of the green emission(520nm) is decreased when x is decreased, and it goes to near zero when x=0nm. This behavior can be identified as the diffusion of the triplet excitons from Ir(ppy)3 to Ir(btp)2 by the Dexter energy transfer(DET). From the external quantum efficiency(EQE) of the red emission, as shown in Fig. 3, the diffusion length of the triplet excitons can be determined by the equation of DET rate, R=A Exp(-2RDA/L), where RDA is donor-acceptor distance and L is the sum of the van der Wals radii. As a result, the measured data of the red EQEs with different x are identified to theoretical result from the equation of DET rate(Fig. 4). From this results, we could confirm that the diffusion length of the triplet excitons can be determined by using DQW structure and this method is very useful to investigate the behavior of the excitons in PHOLEDs.

• Current Photovoltaic Research
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• v.4 no.1
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• pp.1-7
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• 2016

Among the various types of solar cells, silicon based two terminal tandem solar cell is one of the most popular one. It is designed to split the absorption of incident AM1.5 solar radiation among two of its component cells, thereby widening the wavelength range of external quantum efficiency (EQE) spectra of the device, in comparison to that of a single junction solar cell. In order to improve the EQE spectra further and raise short circuit current density ($J_{sc}$) an optimization of the tradeoff between the top and bottom cell is needed. In an optimized cell structure, the $J_{sc}$ and hence efficiency of the device can further be enhanced with the help of light trapping scheme. This can be achieved by texturing front and back surface as well as a back reflector of the device. In this brief review we highlight the development of light trapping in the silicon based tandem solar cell.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.310-310
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• 2009

In the two structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/R-H : R-D/Al device, ITO/Amorphous Fluoropolymers/TPD/R-H : R-D/LiF/Al device. we studied the effect of organic materials defending on the electrical characteristics of red OLEDs. The thickness of TPD and R-H : R-D was manufactured 40 nm, 60 nm, respectively under a base pressure of $5\times10^{-6}$Torr using a thermal evaporation. The AF used for an hole-injection is the thickness of 0.5 [nm] and the LiF used for an electron-injection is the thickness of 0.5 [nm]. Compared to the two from the devices made with the hole injection and without hole injection We found that the luminous efficiency and the external quantum efficiency are improved a fact of one- hundred, two, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.232-237
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• 2014

We have fabricated white organic light-emitting diodes (OLEDs) by co-doping of red and blue phosphorescent guest emitters into the single host layer. Tris(2-phenyl-1-quinoline) iridium(III) [$Ir(phq)_3$] and iridium(III)bis[(4,6-di-fluorophenyl)-pyridinato-$N,C^{2^{\prime}}$]picolinate (FIrpic) were used as red and blue dopants, respectively. The effects of dopant concentration on the emission, carrier conduction and external quantum efficiency characteristics of the devices were investigated. The emissions on the guest emitters were attributed to the energy transfer to the guest emitters and direct excitation by trapping of the carriers on the guest molecules. The white OLED with 5% FIrpic and 2% $Ir(phq)_3$ exhibited a maximum external quantum efficiency of 19.9% and a maximum current efficiency of 45.2 cd/A.

• ETRI Journal
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• v.34 no.5
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• pp.690-695
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• 2012

We investigate the light-emitting performances of blue phosphorescent organic light-emitting diodes (PHOLEDs) with three different electron injection and transport materials, that is, bathocuproine(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) (Bphen), 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (Tm3PyPB), and 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine (26DCzPPy), which are partially doped with cesium metal. We find that the device characteristics are very dependent on the nature of the introduced electron injection layer (EIL) and electron transporting layer (ETL). When the appropriate EIL and ETL are combined, the peak external quantum efficiency and peak power efficiency improve up to 20.7% and 45.6 lm/W, respectively. Moreover, this blue PHOLED even maintains high external quantum efficiency of 19.6% and 16.9% at a luminance of $1,000cd/m^2$ and $10,000cd/m^2$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.496-498
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• 2008

We have developed green phosphorescent organic light-emitting diodes (OLEDs) with high quantum efficiency. Wide-energy-gap material, 1,1-bis[(di-4-tolylamino) phenyl]cyclohexane (TAPC), with high triplet energy level was used as a hole transporting layer. Electrophosphorescent devices fabricated using TAPC as a hole-transporting layer and N,N'-dicarbazolyl-4,4'-biphenyl (CBP) doped with fac-tris(2-phenylpyridine) iridium [Ir(ppy)3] as the emitting layer showed the maximum external quantum efficiency ($\eta_{ext}$) of 19.8 %, which is much higher than the devices adopting 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (NPB) (${\eta}B_{ext}=14.6%$) as a hole transporting layer.