• 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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• 2003.07a
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• pp.948-951
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• 2003

The electroluminescence (EL) properties were studied in organic light-emitting diodes with a red fluorescent dye, 4- (dicyanomethylene)- 2- tert-butyl-6 (1,1,7,7-tetramethyljulolidyl-9-enyl)- 4H- pyran (DCJTB) doped into tris-(8-hydroxyquinoline)aluminum ($Alq_{3}$), rubrene and the mixed matrix of $Alq_3$ and rubrene. The device with DCJTB doped into the $Alq_{3}$:rubrene mixed host shows an efficient red emission from DCJTB with a negligible EL emission from $Alq_{3}$ and a lower EL onset voltage compared to the device with DCJTB doped into the $Alq_{3}$ only host. The quantum efficiency is almost temperature-independent for the device with the $Alq_3:rubrene$ mixed host. The results indicate that recombination of injected electrons and holes occurs on rubrene and subsequent energy transfer to DCJTB dominates in the device with the $Alq_{3}$:rubrene mixed host.

• Journal of Information Display
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• v.9 no.2
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• pp.14-17
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• 2008

A charge trapping host structure was developed to improve the light-emitting efficiency of green phosphorescent organic light-emitting diodes. N, N'-dicarbazolyl-3,5-benzene(mCP) and a spirobifluorene based triplet host(PHl) were co-deposited as hosts in the emitting layer and the device performance was examined according to the composition mCP and PH1. The results showed that the quantum efficiency could be improved by 30 % using a mixed host of mCP and PH1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.177-180
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• 2004

발광층에 Alq3와 rubrene을 mixed host로 사용하고 DCJTB를 형광 dopant로 사용한 다층 박막 구조의 red OLEDs를 제작하였다. 소자의 구조는 $ITO:Anode(120nm)/{\alpha}-NPD:HTL(40nm)/Alq_3+Rubrene(mixed\;host\;1:1)+DCJTB(red\;dopant\;3%)+:EML(20nm)/Alq_3:ETL(40nm)/MgAg(Mg\;5%\;wt):Cathode(150nm)$ 로서 EML내부에 DCJTB를 Totally Doping Method와 Dotted-Line Doping Method의 두 가지 방법으로 도핑 하였다. Mixed host구조에 DCJTB를 6구간으로 나누어 Dotted Line Doping한 소자는 luminance yield가 $9.2cd/A@10mA/cm^2$ 이었다. 이 소자는 DCJTB만을 Totally Doping한 소자의 luminance yield $3.2cd/A@10mA/cm^2$에 비해 약 190%정도의 높은 효율 향상을 보였다. 또한 $10mA/cm^2$에 도달하는 전압은 5.5V Vs. 8.5V로서 mixed host를 사용한 소자에서 약 3V정도 구동전압이 낮아지는 효과가 있었다. 발광 스펙트럼의 Full Width Half Maximum(FWHM)은 각각 56.6nm와 61nm로서 rubrene을 mixed host로 사용한 소자에서 높은 색 순도를 얻을 수 있었다. 이러한 성능의 향상은 $Alq_3$와 혼합된 rubrene에 의한 낮은 전하주 입장벽, 높은 전류밀도에서 나타나는 발광감쇄현상의 감소, 그리고 발광층의 DLD구조에 의한 전하의 trap & confinement 에 따른 발광 exciton의 형성확률이 증가한데서 나타났다고 생각된다.

• Analytical Science and Technology
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• v.17 no.3
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• pp.282-288
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• 2004

Inclusion selectivities of the cyanocadmate host complexes with ammonium oniums, $[Cd_x(CN)_{2x}][onium{\cdot}zG]$ (onium = $NMe_3Et^+$, $NMeEt{_3}^+$ and $NEt{_4}^+$, G = guest), have been investigated for $C_6H_6$ (B), PhMe (T), PhEt (E), ortho (O), meta (M), and para (P) isomers of $C_6H_4Me_2$ as the aromatic guest molecules. From the binary, ternary, quaternary and quinary mixed guests of B, T, E, O, M and P, the order of preference in the $NMe_3Et+$-host is $B{\gg}$T>P${\fallingdotseq}O{\fallingdotseq}M$ and E>O${\gg}P{\fallingdotseq}M$; in the $NMeEt{_3}^+$-host is T>B>P${\gg}O{\fallingdotseq}M$ and E>P${\gg}$M>O; in the $NEt{_4}^+$-host is $B{\gg}T{\fallingdotseq}O{\fallingdotseq}M{\fallingdotseq}P$. However, the $NEt{_4}^+$-host complexes of E, O, M and P mixed-guests were not obtained. These inclusion selectivities were compared to our previous results of the $NMe{_4}^+$-host; T>B>P${\gg}$M>O and E>P${\gg}$M>O.

• Journal of Plant Biology
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• v.5 no.3
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• pp.30-36
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• 1962

The mechanism of synthesis of the toacco mosaic virus(TMV) and the potato virus X(PVX) was investigated using the methods of ultraviolet light irradiation and serological analysis. In vitro irradiation of UV on the infected tobacco juice for 10 minutes caused the infectivity of TMV and PVX to decrease markedly on their respective local lesion indicator hosts, Nicotiana glutinosa L. and Gomphrena globosa L., indicating that UV destroys directly the infectivity of the virus particles. Ten minutes after the UV was irradiated on the leaves of the two indicator hosts before inoculation, the infectivity of TMV decreased as it was irradiated in vitro, whereas that of PVX increased by 26% as compared with the unirradiated control. When the two viruses were mix-inoculated in the common host of tobacco and the synthetic products were analyzed by serological methods for a two week infection period, it was found that both viruses were multiplying more rapidly and abundantly than they were singly inoculated into the same host species. Titers from mixed series were often two times as high as those of singly inoculated series. A mechanism of competition in the synthesis between the mixed viruses in the common host is postulated.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.439-442
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• 2008

A mixed host structure of TCTA and TPBI was used in orange emitting layer and host composition was critical to device performances of PHWOLEDs. PHWOLEDs with TPBI host in orange emitting layer showed high quantum efficiency of 10.3 % at $1000\;cd/m^2$ with little change of CIE coordinates of (0.32, 0.34) from $100\;cd/m^2$ to $10,000\;cd/m^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.427-428
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• 2008

New high efficiency green light emitting phosphorescent devices with emission layers of [TCTA/TCTA:TAZ/TAZ]:Ir$(ppy)_3$ have been fabricated and evaluated in this paper. Among the devices having different thicknesses of TCTA:TAZ mixed layer in the total 300$\AA$-thick host of TCTA(80$\AA$)/TCTA:TAZ (50~100$\AA$)/TAZ, the device with host of TCTA(80$\AA$)/TCTA:TAZ(90$\AA$)/TAZ(130$\AA$) showed the best electroluminescent characteristics with the current density of 95 mA/$cm^2$ and luminance of 25,000 cd/$m^2$ at an applied voltage of 10V. The maximum current efficiency was 52 cd/A under the luminance of 400 cd/$m^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.192-195
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• 2009

We developed highly efficient blue PHOLEDs with reduced roll-off by using a mixed host structure. The balanced charge carrier injection and the distributed recombination zone within emissive layer resulted in a highly stable efficiency roll-off with quantum efficiencies of 20.1 and 18.1 % at a luminance of 1000 and 10000 cd/$m^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.42-45
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• 2009

We report simple structure red phosphorescent devices comprising only single organic layer structure. Maximum current efficiency of 9.44 cd/A and the driving voltage of 5.4 V are obtained in this single layer structure PHOLEDs, respectively. The mixed host system using electron transporting and hole transporting materials doped with $Ir(piq)_3$ provides such high efficiency and reasonable driving voltage. The principal to simplification is the direct charges injection from the metallic electrodes into mixed host materials.