• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.184-187
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• 2009

In this paper, we study effect of charge balance on performance of blue phosphorescent organic light emitting diodes (OLEDs). Charge balance determines the location of recombination zone in the OLEDs. By tuning the charge balance in iridium (III) bis[(4,6-difluorophenyl)-pyridinate-N,C2']picolinate (FIrpic) based blue phosphorescent organic light-emitting devices (PHOLEDs) with a high mobility and high triplet energy electron transporting material, we were able to achieve a high current efficiency of 60 cd/A which is a 3X improvement over previous devices with 3,5'-N,N'-dicarbazole-benzene (mCP) host.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.38-41
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• 2009

We demonstrate a new commercial green phosphorescent organic light emitting device (OLED) in a bottom emission device and top emission microcavity. The bottom and top emitting phosphorescent OLEDs (PHOLED$^{TM}$s) had luminance efficiencies of 60cd/A and 137cd/A respectively, at a luminance of 1,000cd/$m^2$. The top emission microcavity was close to 1953 NTSC color requirements with 1931 CIE color coordinates of 0.231, 0.718. A record green PHOLED lifetime of >3,500hrs to LT95 from 4000cd/$m^2$ is demonstrated for the microcavity device.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.69.2-69.2
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• 2012

Graphene films have a strong potential to replace indium tin oxide anodes in organic light-emitting diodes (OLEDs), to date. However, the luminous efficiency of OLEDs with graphene anodes has been limited by a lack of efficient methods to improve the low work function and reduce the sheet resistance of graphene films to the levels required for electrodes. Here, we fabricate flexible OLEDs by modifying the graphene anode to have a high work function and low sheet resistance, and thus achieve extremely high luminous power efficiencies (37.2 lm/W in fluorescent OLEDs, 102.7 lm/W in phosphorescent OLEDs), which are significantly higher than those of optimized devices with an indium tin oxide anode (24.1 lm/W in fluorescent OLEDs, 85.6 lm/W in phosphorescent OLEDs). We also fabricate flexible white OLED lighting devices using the graphene anode. These results demonstrate the great potential of graphene anodes for use in a wide variety of high-performance flexible organic optoelectronics.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1414-1417
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• 2008

Using a $Ir(ppy)_3$ doped in the TCTA:$Bepp_2$ mixed host and N- and P-doped in TCTA:$Bepp_2$ charge transport layers, an ideal energy level alignment technology is developed. A very low roll-off current efficiency of 7.4 % at a luminance of $10,000\;cd/m^2$ with this technology is demonstrated in green phosphorescent OLEDs.

• 공업화학
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• 제26권6호
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• pp.725-729
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• 2015

유기발광다이오드(organic light emitting diodes, OLEDs)는 높은 효율, 안정성, 신물질 개발과 같은 연구들을 바탕으로 차세대 디스플레이 및 조명으로써의 높은 기술력과 학문적 발전을 달성하였다. 본 논문에서는 hexaazatrinaphthylene (HAT) 유도체들을 OLEDs 소자의 정공주입층으로 사용하여 제작된 고효율의 녹색 인광 OLEDs 소자의 특성을 연구하였다. Indium Tin Oxide (ITO)전극과 정공수송층 사이에 삽입된 박막의 HAT 유도체층은 $1,000cd/m^2$의 구동 조건에서 OLEDs 소자의 외부양자효율을 기존의 8.8%에서 13.6%로, 전류효율을 30.8 cd/A에서 47.7 cd/A로 각각 향상시켰다. 삽입된 HAT 유도체층은 발광층 내부에서 최적화된 전자-정공의 균형을 이루게 하여 소자의 효율 향상에 기여하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1516-1519
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• 2008

We report extremely low doping technology in phosphorescent organic light emitting diodes(PHOLEDs). Highly efficient red PHOLEDs with excellent energy transfer characteristics even under 1 % doping condition have been demonstrated. Results reveal efficient host-dopant system to realize highly efficient PHOLEDs and useful cost saving way by reduction of expensive Ir complex dopants.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.694-697
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• 2007

We demonstrate the use of screen printing in the fabrication of highly efficient phosphorescent polymer organic-light-emitting devices (OLEDs) based on a green-emitting $Ir(ppy)_3$ and a host polymer PVK. We incorporate PBD in the polymer host as an electron-transporting dopant and ${\alpha}-NPD$ as a hole transporting dopant. The best screen printed single-layer device exhibits very high peak luminous efficiency of 63 cd/A at a relatively high operating voltage of 17.1 V at the luminance of $650\;cd/m^2$. We observed the highest luminance of $21,000\;Cd/m^2$ at 35V. Due to the high operating voltage, despite of the high peak luminous efficiency the peak power efficiency was found to be 12.2 lm/W at the luminance of $470\;cd/m^2$ (15.9 V).

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.663-666
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• 2007

High-efficiency red phosphorescent OLEDs employing a novel red emitter and a multifunctional oligofluorene host are reported. With qazIr(acac) as the red phosphorescent dopant, a maximum external quantum efficiency of 19% and maximum power efficiency of 11 lm/W are achieved. In addition, single layer devices using such host and dopant materials have efficiencies up to 13%.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3711-3717
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• 2010

Four orange-red phosphorescent Ir(III) complexes were designed and synthesized based on the benzoylphenylpyridine ligand with a fluorine substituent. Multilayered OLEDs with the device structure, ITO/2-TNATA/NPB/CBP : 8% Ir(III) complexes/BCP/Liq/Al, were fabricated using these complexes as dopant materials. All the devices exhibited orange-red electroluminescence and their electroluminescent properties were quite sensitive to the structural features of the dopants in the emitting layers. Among these, the maximum luminance ($14700\;cd/m^2$ at 14.0 V) was observed in the device containing Ir(III) complex 1 as the dopant. In addition, its luminous, power and quantum efficiency were 11.7 cd/A, 3.88 lm/W and 9.58% at $20\;mA/cm^2$, respectively. The peak wavelength of electroluminescence was 606 nm with CIE coordinates of (0.61, 0.38) at 12.0 V. The device also showed stable color chromaticity with various voltages.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1513-1515
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• 2008

High efficiency phosphorescent organic light emitting devices ($PHOLED^{TM}s$) are now widely used in commercial displays. In this paper we describe some of the work behind the development of high efficiency stable green PHOLEDs capable of fulfilling display specifications.