• 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 KAIS Fall Conference
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• 2010.05a
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• pp.363-365
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• 2010

고분자 발광다이오드(polymer light emitting diode, PLED)는 초박막화, 초경량화가 가능하며 간단한 용액공정 으로 향후 휨성(flexible) 디스플레이로의 응용이 가능할 것으로 기대되고 있다. 본 연구에서는 녹색 고분자 유기 발광다이오드를 제작하고, 효율을 향상 시키고자 이중 발광층을 두어 전기 광학적 특성을 평가하였다. ITO/Glass기판 위에 정공주입층으로 PEDOT:PSS [poly(3,4-ethylenedio xythiophene):poly(styrene sulfolnate)]를 발광물질로는 형광 발광물질인 PVK(poly-vinylcarbazole)와 인광 발광 물질인 Ir(ppy)$_3$[tris(2-phenylpyridine) iridium(III)]를 각각 host와 dopant로 사용하였다. 정공 차단층 및 전자 수송층 두 개의 역할로 사용 가능한 TPBI(1,3,5-tris(2-N-phenylbenzimidazolyl) benzene)를 진공 열증착법으로 막을 형성하였다. 전자주입층으로 LiF(lithium flouride)와 음극으로 Al(aluminum)을 증착하여 최종적으로 ITO/PEDOT:PSS/PVK:Ir(ppy)$_3$/TPBI/LiF/Al 구조를 갖는 녹색 형광:인광 혼합 유기 발광 다이오드를 제작하였다.

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1627-1637
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• 2012

The coupling reaction between 5-bromo-3-phenylbenzo[c]isoxazole and diphenylamine followed by further condensation with a mono-, di- or ter-acetyl aromatic compound in the presence of diphenyl phosphate at $145^{\circ}C$ gave a novel asymmetric diarylquinolines, oligoquinolines with diphenylamine endgroups, and a first generation quinoline dendrimer in 41-82% isolated yield. The electrochemical and photophysical properties of the oligoquinolines were characterized by cyclic voltammograms (CVs) and spectroscopy. All the quinolines emit bright sky blue light due to charge transfer from quinoline group to diphenly amine with very high quantum efficiency (> 90%). Organic light-emitting diodes (OLEDs) were fabricated using these quinolines as emitting materials. Among different device architectures explored, OLEDs with a structure of ITO/PEDOT (40 nm)/TAPC (15 nm)/D-A quinoline (40 nm)/TPBI (30 nm)/LiF (1 nm)/Al using TAPC as an electron blocking layer and TPBI as a hole blocking layer gave the best performance. A high external quantum efficiency in the range of 1.2-2.3% were achieved in all the quinolines with the best performance in BBQA(5). Our results indicate diarylamino-substituted oligoquinoline and dendrimer are promising materials for OLEDs applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.250-250
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• 2012

Organic light-emitting diodes (OLED) and polymer light emitting diodes (PLED) have been regarded as the candidate for the next generation light source and flat panel display. Currently, the most common OLED industrial fabrication technology used in producing real products utilizes a fine shadow mask during the thermal evaporation of small molecule materials. However, due to high potential including low cost, easy process and scalability, various researches about solution process are progressed. Since polymer has some disadvantages such as short lifetime and difficulty of purifying, small molecule OLED (SMOLED) can be a good alternative. In this work, we have demonstrated high efficient solution-processed OLED with small molecule. We use CBP (4,4'-N,N'-dicarbazolebiphenyl) as a host doped with green dye (Ir(ppy)3 (fac-tris(2-phenyl pyridine) iridium)). PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) and TPD (N,N'diphenyl-N,N'-Bis (3-methylphenyl)-[1,1-biphenyl]-4,4'-diamine) are employed as an electron transport material and a hole transport material. And TPBi (2,2',2''-(1,3,5-phenylene) tris (1-phenyl-1H-benzimidazole)) is used as an hole blocking layer for proper hole and electron balance. With adding evaporated TPBi layer, the current efficiency was very improved. Among various parameters, we observed the property of OLED device by changing the thickness of hole transporting layer and solvent which can dissolve organic material. We could make small molecule OLED device with finding proper conditions.

• Journal of the Korean Applied Science and Technology
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• v.29 no.3
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• pp.459-465
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• 2012

We had synthesized a green dopant material based on the binaphthyl group, 7,7'-(2,2'dimethoxy-1,1'-binaphthyl-3,3'-diyl) bis(4-(thiophen -2-yl) benzo[e][1,2,5] thiadiazole (TBT). We also fabricated the white organic light emitting diode (OLED) with a phosphorescent blue emitter : iridium(III)bis[(4,6-di-fluoropheny)-pyridinato -N,C2]picolinate (FIrpic) doped in N,N'-dicarbazolyl-3,5-benzene (mCP) of hole transport type host material and both TBT and bis(2-phenylquinolinato)- acetylacetonate iridium(III) (Ir(pq)2acac) doped in 1,3,5-tris(N-phenylbenzimidazole -2-yl)benzene (TPBi) of electron transport type host material. As a result, the property of white OLED using TBT, which demonstrated a maximum luminous efficiency and external quantum efficiency of 5.94 cd/A and 3.23 %, respectively. It also showed the pure white emission with Commission Internationale de I'Eclairage (CIE) coordinates of (0.34, 0.36) at 1000 nit.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.230.1-230.1
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• 2016

본 연구에서는 Host-Dopant system 기반 적색 인광 OLED의 Emitting layer(EML)에서 doping 위치에 따른 특성 변화를 분석하였다. EML은 host 물질로 60 nm 두께의 CBP를 사용하고, 적색 발광을 위해 10 %의 $Ir(btp)_2$를 CBP의 Front, Middle, Back side에 각각 20 nm씩 doping하였다. 본 구조의 적색 인광 OLED는 current density, luminance, efficiency, EL spectrum 등을 통해 전기적, 광학적 특성 변화를 확인하였다. Front, Back side에 doping으로 인한 CBP의 Energy level이 3.6 eV에서 1.9 eV로 감소하여 각각 HTL/EML, EML/HBL의 경계에 carrier direct injection이 활성화 되었고, 이로 인한 charge balance의 저하를 확인하였다. EL spectrum결과 각 소자는 CBP의 618 nm 파장 외에도, 추가적으로 TPBi의 398 nm, NPB의 456 nm의 파장을 보였다. 이를 통해 doping 위치에 따라 exciton이 형성되는 recombination zone이 이동하고 있음을 확인하였고, Front side는 6 V의 인가전압에서는 발광 파장이 398 nm에서 높은 값을 보이나 8 V, 10 V, 12 V에서 618 nm에서 높은 값을 보이는 것으로 인가전압에 의해 recombination zone이 HTL쪽으로 이동되는 것 또한 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.151.2-151.2
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• 2015

본 연구에서는 indium-tin-oxide(ITO)/1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile(HAT-CN)/N,N'-di(naphthalene-lyl)-N,N'-diphenyl-benzidine(NPB)/4,4'-Bis(N-carbazolyl)-1,1'-biphenyl(CBP)/2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)TPBi/tris-(8-hydroxyquinoline) aluminum($Alq_3$)/LiF/Al 구조를 가진 유기 발광 다이오드 소자의 발광층에 $Ir(ppy)_3$(2% wt)을 도핑하여 소자의 특성 변화를 살펴보았다. $Ir(ppy)_3$의 두께는 5nm이고 도핑 위치는 정공 수송층과 발광층 계면의 0nm에서부터 25nm까지 5nm간격으로 도핑을 하였다. 실험 결과 소자의 효율은 도핑 위치가 정공 수송층에서 25nm떨어진 위치일 때 가장 높았고, 10nm일 때 가장 낮았다. 이는 도핑 부분의 위치가 정공 차단층에 가까워질수록 정공과 전자의 균형이 좋아지는 것이 소자 성능을 향상시키는 원인으로 추측된다.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1366-1370
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• 2013

A series of phosphorescent iridium(III) complexes 1-4 based on phenylpyrazole were synthesized and their photophysical properties were investigated. To evaluate their electroluminescent properties, OLED devices with the structure of ITO/NPB/mCP: 8% Iridium complexes (1-4)/TPBi/Liq/Al were fabricated. Among those, the device with 3 showed the most efficient white emission with maximum luminance of 100.6 $cd/m^2$ at 15 V, maximum luminous efficiency of 1.52 cd/A, power efficiency of 0.71 lm/W, external quantum efficiency of 0.59%, and CIE coordinates of (0.35, 0.40) at 15.0 V, respectively.

• Journal of the Korean Applied Science and Technology
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• v.34 no.3
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• pp.562-567
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• 2017

The organic light-emitting diodes are fabricated with six anthracene derivatives containing simple substituents such as phenyl or naphthyl group. The device structure is as in the following: Indium tin oxide (ITO) (180 nm)/4,4-4,4',4"-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (2-TNATA) (30 nm)/4,4'-bis[N-(1-naphthyl)-N-phenyl-1-amino] biphenyl (NPB) (20 nm)/Emitting compound (30 nm)/2,2',2"-(1,3,5-Benzinetriyl)-tris (1-phenyl-1-H-benz-imidazole) TPBi (40 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). In the emitting layer the anthracene derivatives are used without any dopant. All the six devices show blue emissions. Among the tested diodes, the one with 9-(2-naphthyl)-10-(p-tolyl) anthracene (2-NTA) exhibited luminous efficiency, power and external quantum efficiencies of 3.26 cd/A, 0.98 lm/A, 2.8 % at $20mA/cm^2$.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.4
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• pp.79-83
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• 2011

White phosphorescence polymer light emitting diodes (WPhPLEDs) with a glass/ITO/PEDOT:PSS/PFO:$Ir(ppy)_3$:MDMO-PPV/TPBI/LiF/Al structure were fabricated to investigate the effects of $Ir(ppy)_3$ doping concentrations on the optical and electrical properties of the devices. PFO, $Ir(ppy)_3$ and MDMO-PPV conjugated polymers as host and guest materials in the emission layer were spin coated at various concentrations of $Ir(ppy)_3$ ranging from 0.0 to 20.0 vol.%. As the concentration of $Ir(ppy)_3$ increased from 5.0 to 20.0 vol.%, the luminance and current efficiency values of the devices decreased clearly, which are attributable to the quenching effect at a high doping concentration. The maximum luminance and current density were 2850 $cd/m^2$ and 741 $mA/cm^2$, respectively for a WPhPLED with an $Ir(ppy)_3$ concentration of 5.0 vol.%. The CIE color coordinates were about x=0.33 and y=0.34 at 11V, showing a good white color.