• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.817-819
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• 2009

We have developed highly efficient blue phosphorescent organic light-emitting devices (PHOLEDs) with simplified architectures using new host materials. The Blue PHOLED with new host:FIrpic emitting layer exhibits a maximum luminance efficiency of 34 cd/A and a low operating voltage 5 V at a high luminance of 1212 cd/$m^2$.

• ETRI Journal
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• v.31 no.6
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• pp.642-646
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• 2009

Highly efficient white phosphorescent organic light-emitting diodes with a mixed-host structure are developed and the device characteristics are studied. The introduction of a hole-transport-type host (N, N'-dicarbazolyl-3-3-benzen (mCP)) into an electron-transport-type host (m-bis-(triphenylsilyl)benzene (UGH3)) as a mixed-host emissive layer effectively achieves higher current density and lower driving voltage. The peak external quantum and power efficiency with the mixed-host structure improve up to 18.9% and 40.9 lm/W, respectively. Moreover, this mixed-host structure device shows over 30% enhanced performance compared with a single-host structure device at a luminance of 10,000 $cd/m^2$ without any change in the electroluminescence spectra.

• 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.

• Transactions on Electrical and Electronic Materials
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• v.11 no.2
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• pp.85-88
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• 2010

Deep blue organic light emitting diodes (OLEDs) were fabricated using 5 wt.% doped BCzVBi with various blue host materials such as NPB, DPVBi, MADN and TPBi. A blue OLED device, using DPVBi as host material, was constructed via NPB ($500\;{\AA}$) / DPVBi:BCzVBi ($200\;{\AA}$) / Bphen ($300\;{\AA}$) / LiF ($20\;{\AA}$) / Al ($1,000\;{\AA}$) and it shows a maximum luminescence of $4,838\;cd/m^2$, a current density of $32.7\;mA/cm^2$, a luminous efficiency of 3.3 cd/A and CIExy coordinates of (0.19, 0.15) at 4.5 V whereas the luminous efficiencies and CIExy coordinates of other blue OLEDs using NPB, MADN and TPBi as host materials have 1.1, 2.6 and 2.0 cd/A and (0.15, 0.11), (0.15, 0.10) and (0.15, 0.10), respectively. Energy transfer mechanisms between BCzVBi and its host materials were discussed with an energy band structure of host materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.29-30
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• 2008

New spiro-type host materials, 5'-phenylnaphthyl-spiro[fluorene-7,9'-benzofluorene](BH-lPN) and 5',6-bis(phenylnaphthyl)-spiro[fluorene-7,9'-benzofluorene](BH-6PN) were designed and successfully prepared by the Suzki reaction. The EL characteristics of BH-1PN as blue host material doped with blue dopant materials, BD-1 were evaluated and compared with the existing host MADN:dopant BD-1 system. The structure of the device is ITO/DNTPD/NPB/Host:5% dopant/Alq3/Al-LiF. The device obtained from BH-lPN doped with BD-1 showed a good color purity and efficiency, on the other hand luminance and current-density characteristics are worse than that of MADN doped with BD-1.

• Journal of Information Display
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• v.8 no.2
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• pp.15-19
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• 2007

We have studied the effect of host materials on the electrophosphorescence properties by comparing three different host materials such as tris(8-hydroxyquinoline)-aluminum (III) $(Alq_3)$, bis(8-hydroxyquinoline)-zinc (II) $(Znq_2)$, and 4,4'-N,N' dicarbazole-biphenyl (CBP) doped with a red-emissive phosphorescent dye, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum (II) (PtOEP). The EL spectra show a strong red emission (peak at 650 nm) from the triplet excited state of PtOEP and a very weak emission from an electron transport layer of $Alq_3$ and a hole transport layer of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1-biphenyl-4,4'-diamine (TPD). We find that the triplet exciton lifetime and the quantum efficiency decrease in the order of CBP, $Alq_3$, and $Znq_2$ host materials. The results are interpreted as a poor exciton confinement in $Alq_3$, and $Znq_2$ host compared with in CBP. Therefore, it is very important for the triplet-exciton confinement in the emissive layer for obtaining a high efficiency.

• ETRI Journal
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• v.33 no.1
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• pp.32-38
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• 2011

We investigated the light-emitting performances of blue phosphorescent organic light-emitting diodes, known as PHOLEDs, by incorporating an N,N'-dicarbazolyl-3,5-benzen interlayer between the hole transporting layer and emitting layer (EML). We found that the effects of the introduced interlayer for triplet exciton confinement and hole/electron balance in the EML were exceptionally dependent on the host materials: 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole, and 4,4'-bis-triphenylsilanyl-biphenyl. When an appropriate interlayer and host material were combined, the peak external quantum efficiency was greatly enhanced by over 21 times from 0.79% to 17.1%. Studies on the recombination zone using a series of host materials were also conducted.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1475-1482
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• 2011

New spiro[benzo[c]fluorene-7,9'-fluorene] (SBFF)-based blue host materials, 9-phenyl-SBFF (BH-4P) and 5,9-diphenyl-SBFF (BH-6DP), were successfully prepared by spiro-formation of 9-phenyl-7H-benzo[c]fluoren-7-one with 2-bromobiphenyl via lithiation and reaction of 5,9-dibromo-SBFF with phenylboronic acid through the Suzuki reaction, respectively. Diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)-phenyl]-amine (BD-1) and N,N-diphenyl-N',N'-diphenyl-SBFF-5,9-diamine (BD-6DPA) were used as dopant materials. Blue OLEDs with the configuration ITO/N,N'-bis-[4-(di-m-tolylamino)phenyl]-N,N'-diphenylbiphenyl-4,4'-diamine (DNTPD)/bis[N-(1-naphthyl)-N-phenyl]benzidine (NPB)/host:5% dopant/SFC-137/Al-LiF were prepared from the two host materials doped with BD-1 and BD-6DPA dopants and the devices composed of BH-4P and BH-6DP doped with BD-6DPA showed blue EL spectra at 458 and 463 nm at 7 V and luminance efficiencies of 4.58 and 4.88 cd/A, respectively.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.399-405
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• 2013

Two series of new green phosphorescent polymers bearing a bis(2-phenyl-pyridine)iridium(III)(dibenzoylmethane) [$(ppy)_2Irdbm$] complex were designed and synthesized. Poly-carbazole (PCbz) derivative or polyfluorene with pendant carbazole groups (PFCbz) were employed as host polymers for the iridium complex. The iridium complex monomer was copolymerized with the host monomers using varying monomer ratios via a Yamamoto coupling reaction. Efficient energy transfer from host to dopant unit was observed by increasing the ratio of the iridium guest in the copolymers. Electroluminescent devices with the configuration ITO/PEDOT:PSS/polymer/BmPyPB/LiF/Al were fabricated and characterized. The phosphorescent polymers composed of the iridium complex guest and polyfluorene with carbazole pendants as a host performed better than the polymers composed of the same guest and the main chain polycarbazole host. A maximum external quantum efficiency of 0.73%, a luminous efficiency of 1.21 cd/A, and a maximum luminance of 372 $cd/m^2$ were obtained from a device fabricated using one of the synthesized copolymers.

• Journal of Integrative Natural Science
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• v.3 no.2
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• pp.78-83
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• 2010

DBR/Host dual porous silicons containing DBR and host structure were prepared and their optical properties were characterized using Ocean Optics spectrometer. In this dual porous silicon, single porous silicon layer was used as host layer for possible biomolecule and drug materials and DBR porous silicon layer was used for signal transduction due to the recognition of molecules. Optical reflection spectrum of dual porous silicon displayed only DBR reflection but Fabry-Perot fringe pattern. DBR reflection band of dual porous silicon shifted to the shorter wavelength as the etching time of host layer increased. Cross-sectional FE-SEM image of dual porous silicon displayed a thickness of about 20 micrometer for DBR porous silicon layer. Developed etching technology could be useful to prepare DBR porous silicon which exhibited specific reflection resonance at the required wavelength and to provide an label-free biosensors and drug delivery materials.