• Bulletin of the Korean Chemical Society
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• v.26 no.10
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• pp.1569-1574
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• 2005

To develop new hole-blocking materials for phosphorescent organic light-emitting diodes (PhOLEDs), 5,6-dihydro-2,9-diisopropyl-4,7-diphenyl[1,10]phenanthroline (1) and 5,6-dihydro-2,9-diisopropyl-4-(4-methoxyphenyl)-7-phenyl[1,10]phenanthroline (2) were synthesized. While the absorption spectrum of 1 is very similar to that of 2, the photoluminescence spectrum of 1 has the feature of the narrower and blue-shifted blueviolet emission at the peak of 356 nm compared to that of 2. The HOMO and LUMO energy levels of 1 and 2 were estimated from the measurement of cyclic voltammetry, and 1 has the appropriate levels for a holeblocking layer (HBL). The use of 1 as a HBL in a green PhOLED led to good efficiency of 23.6 cd/A at 4.4 mA/$cm^2$.

• 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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• 2007.08a
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• pp.239-244
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• 2007

Highly efficient and stable white PIN OLED structures have been developed with a focus on possible AM display applications. Due to the use of the novel air-stable Novaled n-dopant material NDN26, the mass production compatibility of the PIN approach is improved. With both a conventional n-dopant, NDN1, and a novel air-stable n-dopant, NDN26, similar performance in efficiency and lifetime are reached. Based on highly a stable red fluorescent emitter system, the Novaled PIN approach allows for reaching ultra-long lifetimes of 1,000,000 hours at a brightness of $1,000\;cd/m^2$, both for top and for bottom emission layouts. Furthermore, inverted PIN structures for a possible use in a-Si backplane applications for AM displays are shown. With a phosphorescent green emitter system it could be demonstrated that for bottom and inverted as well as non-inverted top emission, a brightness of $1,000\;cd/m^2$ can be reached at below 3 V. In addition to low operating voltages and long lifetimes, PIN OLEDs also enable for device structures with extremely low operating voltage drifts, a feature of increasing importance for future AM display developments.

• Applied Chemistry for Engineering
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• v.27 no.5
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• pp.455-466
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• 2016

Organic light-emitting diode (OLED) has drawn a lot of attention in academic and industrial fields, which has been successfully commercialized in mobile phones and TV's. In the field of lighting, unlike the existing incandescent or fluorescent lighting, OLED has distinctive qualities such as surface lighting-emission, large-area, lightweight, ultrathin, flexibility in addition to low energy use. This article introduces prominent fluorescent, phosphorescent, and luminescent materials applied to white OLED (WOLED). The understanding and systematic classification of previously studied substances are expected to be greatly helpful for the development of new luminous materials in future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.4
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• pp.397-402
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• 2023

We have developed inverted green phosphorescent organic light emitting diodes (OLEDs) using 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and bis(carbazole-9-yl)biphenyl (CBP) hole transport layers. The driving voltage, current efficiency, power efficiency, and emission characteristics of devices were investigated. While the driving voltage for the same current density was about 1~2 V lower in the devices with the TAPC layer, the maximum luminance was higher in the device with the CBP layer. The maximum current efficiency and power efficiency were 3.2 and 2.7 times higher in the device with the CBP layer, respectively. The higher efficiency in the CBP device resulted from the enhanced hole-electron balance although weak parasitic recombination takes place in the CBP hole transport layer.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.1-6
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• 2008

New devices with the structure of ITO/2-TNATA/NPB/TCTA/CBP:$7%Ir(ppy)_3$/BCP/SFC-137/LiF/Al were designed and fabricated to develop high efficiency green phosphorescent organic light emitting diodes and their electroluminescence properties were evaluated. Among the devices with different thicknesses of CBP in a range of $150{\AA}{\sim}350{\AA}$, the best luminance was obtained in the device with $300{\AA}$-thick CBP host. Nearly saturated current efficiencies indicates that the maximum efficiency value can be obtained with CBP thicknesses of $300{\AA}{\sim}350{\AA}$. The current density, luminance, and current efficiency of the PhOLED(phosphorescent organic light emitting diode) with $CBP(300{\AA}):7%Ir(ppy)_3-emissive$ layer at an applied voltage of 10V were $40mA/cm^2,\;10000cd/m^2$, and 25 cd/A, respectively. The maximum current efficiency was 40.5cd/A under the luminance of $160cd/m^2$. The peak wavelength and FWHM(full width at half maximum) in the electroluminescence spectral were 512nm and 60nm, respectively. The color coordinate was (0.28, 0.63) on the CIE (Commission Internationale de I'Eclairage) chart.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.61-65
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• 2015

We have fabricated poly(3,4-ethylenedioxythiophene) : poly(4-styrenesulfonate) (PEDOT : PSS) thin films using a slotdie coater for the applications of OLED lightings. It is demonstrated that the properties of slot-die coated PEDOT : PSS films are comparable with those of spin-coated ones. Namely, the average and peak-to-peak roughness of the slot-die coated 50-nm-thick PEDOT : PSS film are measured to be as low as 0.247 nm and 1.3 nm, respectively. Moreover, we have obtained excellent thickness uniformity (~1.91%). With the slot-die coated PEDOT : PSS films, we have fabricated green phosphorescent OLED devices. For comparison, we have also fabricated OLED devices with spin-coated PEDOT : PSS films. Both show almost no discrepancy in device performance. The power efficiency (25.4 lm/W) and emission uniformity (77%) of OLEDs with slot-die coated PEDOT : PSS films are shown to be slightly lower than those (27.3 lm/W, 80%) of OLEDs with spin-coated PEDOT : PSS films at the luminance of 1,000nit, increasing the feasibility of using a slot-die coating process for the fabrication of large-area OLED lighting sources at a competitive price.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.454-457
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• 2008

We report the syntheses, photophysical properties and device performances of solution processible host material for green-phosphorescent OLEDs. The butterfly-shaped new host materials with nonconjugated linkage of carbazole and fluorene moieties have large triple energy band gap around 2.8 eV. All of the EL devices exhibited turn-on voltages in the range of 4.8-5.0 V. GH-4 exhibited the best performance with a maximum current efficiency and power efficiency of 21.1 cd/A and 7.9 lm/W.

• 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.

• Journal of IKEEE
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• v.24 no.3
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• pp.706-712
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• 2020

To improve light-emitting performance of green phosphorescent organic light-emitting diodes (OLEDs), we introduced new hole injection materials-hexaazatrinaphthylene (HATNA) derivatives as a solution processed hole injection layer (HIL). The HATNA derivative has a low the lowest unoccupied molecular orbital (LUMO) energy level, similar to the work function of Indium Tin Oxide (ITO), showing a different concept of hole injection mechanism. It was confirmed that the device efficiency of OLEDs using HATNA-HIL showed the improved external quantum efficiency from 10.8% to 15.6% and current efficiency from 32.7 cd/A to 42.7 cd/A due to the balance of electrons and holes in the emissive layer.