• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.9
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• pp.802-807
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• 2007

We have developed red phosphorescent top emission organic light-emitting diodes with transparent metal cathodes deposited by using thermal evaporation technique. Phosphorescent guest molecule, BtpIr(acac), was doped in host CBP for the red phosphorescent emission, Ca/Ag, Ba/Ag, and Mg/Ag double layers were used as cathode materials of top emission devices, which were composed of glass/Ni/2TNATA(15 nm)/${\alpha}$-NPD(35 nm)/CBP:BtpIr(acac)(40 nm, 10%)/BCP(5 nm)/$Alq_3$(5 nm)/cathodes. The optical transparencies of these metal cathodes strongly depend on underlying Ca, Ba, and Mg layers. These layers also strongly affect the electrical conduction and emission properties of the red phosphorescent top emission devices.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.84-87
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• 2011

We fabricated phosphorescent organic light-emitting devices with a 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) host layer. Two kinds of devices, one of ITO/TAPC/TAPC:FIrpic/TAZ/LiF/Al (device A) and one of ITO/TAPC:FIrpic/TAPC/TAZ/LiF/Al (device B), were prepared to investigate electrical and optical properties. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,$C^{2'}$]picolinate (FIrpic) and 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ) were used as a blue phosphorescent guest material and an electron transport layer, respectively. The TAPC layer in device B strongly contributes to whitish emission, higher driving voltage, and lower current efficiency characteristics compared with device A. The mechanisms of these electrical and optical characteristics of the devices were investigated.

• Journal of Information Display
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• v.12 no.3
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• pp.141-144
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• 2011

To improve the performance of blue fluorescent and green phosphorescent organic light-emitting diode devices, Merck developed novel green phosphorescent host and electron-transporting materials. The newly developed electron-transporting material improves the external quantum efficiency of blue fluorescent devices up to 8.7%, with an excellent lifetime. In combination with the newly developed host materials, the efficiency of green phosphorescent devices can be improved by a factor of 1.7, and the lifetime by a factor of 7.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.188-192
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.454-457
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• 2008

We report the syntheses, photophysical properties and device performances of solution processible host material for green-phosphorescent OLEDs. The butterfly-shaped new host materials with nonconjugated linkage of carbazole and fluorene moieties have large triple energy band gap around 2.8 eV. All of the EL devices exhibited turn-on voltages in the range of 4.8-5.0 V. GH-4 exhibited the best performance with a maximum current efficiency and power efficiency of 21.1 cd/A and 7.9 lm/W.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.171-174
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• 2008

We present results demonstrating that low power consumption phosphorescent AMOLED displays can be fabricated on ultra-thin ($25{\mu}m$) stainless steel substrates, combining an amorphous silicon backplane with a top emission phosphorescent OLED frontplane. We will present preliminary results of flexibility testing on these displays.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.925-927
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• 2008

In order to improve the performance in green phosphorescent OLED devices, Merck has developed novel host and electron blocking materials. The newly developed host materials improve the device lifetime by a factor of 3. The newly developed electron blocking materials having not only electron but also exciton barrier properties increase the efficiency of the device by a factor of 1.4. Comparable results were achieved in phosphorescent red systems with further host materials.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1143-1146
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• 2005

Novel series of electron-transporting hosts, pentavalent aluminum complexes containing 8 hydroxyquinoline ligands and various phenolato ligands were synthesized, and organic light-emitting diodes (OLEDs) were fabricated using these complexes as host materials of phosphorescent emitting device and the fabricated phosphorescent emitting device showed low driving voltage, high efficiency at high current density and good stability under conventional driving condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.214-217
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• 2002

The internal quantum efficiency of organic light emitting devices(OLEDs) using fluorescent organic materials is limited within 25% because of the triplet excitons which can hardly emit light. So there has been considerable interest in finding ways to obtain light emission from triplet excitons. One approach has been to add phosphorescent compounds to one of the layers in OLEDs. Then triplet excitons can transfer to these phosphorescent molecules and emit light. In this study, multilayer OLEDs with phosphorescent emitter, Iridium complexes were prepared. The devices with a structure of ITO/TPD/Ir complex doped in the host material/Alq3/Li:Al/Al were fabricated, and its electrical and optical characteristics were studied. Using various Ir complexes and the host materials, we fabricated several devices and investigated the device characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.155-155
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• 2010

We have investigated organic light-emitting devices by doping phosphorescent orange and fluorescent blue emitters into the separate layers of single host. The electroluminescence spectra and current efficiency were strongly dependent on the location of each doped layers. The luminance-voltage (L-V) characteristics of the device2 (ITO/Hole Transport Layer/Orange Phosphorescent emissive layer/Blue Fluorescent emissive layer/Electron Transport Layer/liF/Al) showed the maximum current efficiency of 19.5 cd/A.