• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.166-166
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• 2006

The photoluminescence (PL) efficiency of $Ir(ppy)_{3}$:PVK is lower than $Ir(ppy)_{3}$:CBP for the whole range of doping concentration and this low PL efficiency can be a reason of the lower efficiency of PhPLED than PhOLED. The lower efficiency is originated from the large bi-excitonic quenching such as the triplet-triplet annihilation. The PhPLEDs showed very short lifetime. The short lifetime was found to be originated from the instability of the doubly reduced $Ir(ppy)_{3^{-2}}$. The double reduction takes place because of the low electron mobility of PVK and large energy difference of LUMO level between PVK and $Ir(ppy)_{3}$.

• 한국전기전자재료학회논문지
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• 제24권8호
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• pp.678-681
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• 2011

We have investigated the effect of organic thin film on the driving voltage of OLED (organic light emitting diode) by inserting a 5 nm thick 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) or triphenylphosphineoxide ($Ph_3PO$) between tris-(8-hydroxyquinoline)aluminum ($Alq_3$) electron transport layer and 4,4'-bis(2,2'-diphyenylvinyl)-1,1'-biphenyl (DPVBi) emission layer. The device with 5 nm thick $Ph_3PO$ layer exhibited higher maximum current efficiency and lower driving voltage than the device with BCP layer, resulting from better electron injection from $Alq_3$ to DPVBi in the device with $Ph_3PO$ layer.

• 한국전기전자재료학회논문지
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• 제19권9호
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• pp.878-882
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• 2006

We have fabricated single organic layer devices of the organolanthanide complex, terbium tris-(1-phenyl-3-methyl-4-(tertiarybutyry)pyrazol-5-one)triphenylphosphine oxide [$(tb-PMP)_{3}Tb-(Ph_{3}PO)$] for the investigation of its light emission and electrical conduction properties. The thickness of ($(tb-PMP)_{3}Tb-(Ph_{3}PO)$) layer was varied to 60, 75, 95 nm. Mg and Ca layers were used for the cathode contact. The electrical conduction in the $(tb-PMP)_{3}Tb-(Ph_{3}PO)$ single layer devices was dominated by the injection of electrons into the organic layer from the cathode. A higher current density at much lower voltages can be attained with Ca cathode because of the enhanced electron injection. The device shows very sharp emission at 548 nm. The FWHM of the strongest emission peak was 12 nm.

• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.252-256
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• 2009

We have developed low driving voltage white organic light emitting diode with a new electron transport material, triphenylphosphine oxide ($Ph_{3}PO$). The white light emission was realized with a rubrene yellow dopant and blue-emitting DPVBi layer. The new electron transport layer results in a very high current density at low voltage, resulting in a reduction of driving voltage. The device with a new electron transport layer shows a brightness of $1150\;cd/m^2$ at a low driving voltage of 4.3 V.

• 마이크로전자및패키징학회지
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• 제15권2호
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• pp.1-6
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• 2008

고효율 녹색 인광 유기발광다이오드를 개발하기 위해 소자 구조를 ITO/2-TNATA/NPB/TCTA/CBP:$7%Ir(ppy)_3$/BCP/SFC-137/LiF/Al로 설계 제작하고 그 전계발광 특성을 평가하였다. 소자 제작에서 발광 호스트의 두께를 $150{\AA}{\sim}350{\AA}$ 범위로 변화시켜, 전계발광 특성을 비교해 본 결과, CBP두께가 약 $300{\AA}$ 부근일 때 가장 우수한 휘도 특성이 얻어졌다 전류 효율은 CBP두께가 $300{\AA}{\sim}350{\AA}$범위일 때 거의 포화되어 최대로 나타났다. $CBP(300{\AA}):7%Ir(ppy)_3-EML$ 층을 갖는 PhOLED(phosphorescent organic light emitting diode)의 전류 밀도, 휘도, 그리고 전류 효율은 10V의 인가전압에서 각각 $40mA/cm^2,\;10000cd/m^2$, 25cd/A로 나타났다. 또한 이 소자의 최대 전류효율은 $160cd/m^2$의 휘도 상태에서 40.5cd/A로 나타났다. 발광 스펙트럼은 512nm의 중심 파장과 약 60nm의 FWHM(Full Width Half Maximum)을 나타내었으며, CIE (Commission Internationale de I'Eclairage)도표 상에서 색 좌표는 (0.28,0.63)으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.351-352
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• 2008

A new high efficient red PhOLED using a host of $Bebq_2$ and double dopants of $(pq)_2$Ir(acac) and SEC-R411 have been fabricated and evaluated. The device doubly doped with $(pq)_2$Ir(acac) and SFC-R411 showed the current efficiency improvement of 22% under a luminance of 10000 cd/$m^2$ in comparision with the device singly doped with SFC-R411. The luminance, current efficiency and central wavelength of the doubly doped device were 9300 cd/$m^2$ at 7V, 11.1 cd/A under a luminance of 10000 cd/$m^2$ and 625 nm, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 학술대회 및 기술세미나 논문집 디스플레이 광소자
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• pp.83-84
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• 2006

ITO/4, 4', 4"-tris (N -3 - methylphenyl - N - phenyl - amino) - triphenylamine, [m-MTDATA] / Terbium Iris - (1 - phenyl - 3 - methyl - 4 - (tertiarybutyryl) - pyrazol - 5 - one) triphenylphosphine oxide [$(tb-PMP)_3Tb-(Ph_3PO)$] / Mg:Ag devices were made to investigate its electrical and light emission properties. The thickness of m-MTOATA layer was varied from 0 to 80 nm. There was a threshold thickness for the sufficient hole injection. The insertion of 20 nm thick m-MTDATA layer between ITO and Tb-complex resulted in the right shift of current-voltage curve because of the insufficient hole injection. The low operating voltage can be obtained above the 40 nm of m-MTDATA layer. The insertion of m-MTDATA induced the increase of the background in the electroluminescence spectrum which was dependent on the current density of the devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.412-413
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• 2006

The electrical conduction mechanism of ITO / Terbium tris - (1 - phenyl - 3 - methyl - 4 - (tertiarybutyryl) - pyrazol - 5 - one) triphenylphosphine oxide [$(tb-PMP)_3Tb-(Ph_3PO)$]/Mg/Al devices has been investigated. The calculation of electric field in single layer organic layer between cathode and anode shows the uniform distribution for the electron injection barrier of over 1.4 eV. The measured current-voltage curve shows well matching with the calculated curve based on the tunneling injection of electron under the uniform distribution of electric field.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권2호
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• pp.1654-1657
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• 2007

We demonstrate that the reduction of quantum efficiency with increasing current density in phosphorescent light emitting diodes (PhOLEDs) is related to the formation of excitons in hole transporting layer based on the analysis of emission spectra and exciton formation zone. By employing dual emitting layerm we could achieve maintaining quantum efficiency at high current density up to $10000\;cd/m^2$ as 13.1% compared to the devices with single emitting layer (S-EML) (${\eta}_{ext}$= 6.9% at $10000\;cd/m^2$).

• 한국재료학회:학술대회논문집
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• 한국재료학회 2008년도 춘계학술발표대회 및 제14회 신소재 심포지엄
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• pp.37.1-37.1
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• 2008