• Journal of the Semiconductor & Display Technology
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• v.7 no.3
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• pp.5-9
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• 2008

New devices with structure of ITO/2TNATA/NPB/TCTA/CBP:7%Ir(ppy)$_3$/BCP/ETL/LiF/Al were proposed to develop high luminous green phosphorescent organic light emitting diodes and their electroluminescent properties were evaluated. The experimental devices were divided into two kinds according to the material ($Alq_3$ or SFC137) used as an electron transport layer (ETL). Luminous intensities of the devices using $Alq_3$ and SFC137 as electron transport layers were 27,500 cd/$m^2$ and 51,500 cd/$m^2$ at an applied voltage of 9V, respectively. The current efficiencies of both devices were similar as 12.6 cd/A under a luminance of 10,000 cd/$m^2$, while showed slower decay in the device with SFC137 as an ETL according to the further increase of luminance. Current density and luminance of the device with SFC137 as an electron transport layer were higher at the same voltage than those of the device with $Alq_3$ as an ETL.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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• pp.23-26
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• 2007

The effects of plasma treatment on the ITO/glass substrate before deposition of organic materials were investigated in the fabrication of green light emitting organic devices with $Alq_3-C545T$ fluorescent system. In our experiments, the optimum plasma treatment was obtained at the power and time of 150W and 2 minutes under the $Ar(50%)/O_2$ ambient of 1 mTorr. The green OLED with plasma treatment at 150W for 2 minutes showed the luminance and efficiency of $4700\;cd/m^2$ and 8 lm/W at 10V, respectively. On the contrary, the same structured device without plasma treatment showed much lower performance with the luminance of $2600\;cd/m^2$ and the efficiency of 3.6 lm/W at 10 V.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1425-1428
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• 2007

The amorphous IZO on flexible substrate (PC) shows similar electrical conductivity and optical transmittance with commercial ITO glass even though it was prepared at $<50\;^{\circ}C$. Moreover, it exhibits little resistance change during 5000 bending cycles, demonstrating good mechanical robustness. A green phosphorescent OLED fabricated on amorphous IZO on flexible PC shows maximum external quantum efficiency of ${\eta}_{ext}=13.7\;%$ and power efficiency of ${\eta}_p=32.7\;lm/W$, which are higher than a device fabricated on a commercial ITO on glass (${\eta}_{ext}=12.4%$ and ${\eta}_p=30.1\;lm/W$) and ITO on flexible PC (${\eta}_{ext}=8.5%$ and ${\eta}_p=14.1\;lm/W$).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.641-646
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• 2005

To fabricate a single layer white organic light emitting diode (OLED), a novel non-conjugated blue emitting material PPPMA-co-DTPM copolymer was synthesized containing a perylene moiety unit with hole transporting and blue emitting ability and a triazine moiety unit with electron transporting ability. The devices were fabricated using PPPMA-co-DTPM $(PPPMA[70\;wt\%]:DTPM[30\;wt\%])$ copolymer by varying the doping concentrations of each red, green and blue fluorescent dye, by molecular-dispersing into Toluene solvent with spin coating method. In case of ITO/PPPMA-co-DTPM:TPB$(3\;mol\%):C6(0.04\;mol\%):NR(0.015\;mol\%)/Al$ structure, as they were molecular-dispersing into 30 mg/ml Toluene solvent, nearly-pure white light was obtained both (0.325, 0.339) in the CIE coordinates at 18 V and (0.335, 0.345) at 15 V. The turn-on voltage was 3 V, the light-emitting turn-on voltage was 4 V, and the maximum external quantum efficiency was $0.667\%$ at 24.5 V. Also, in case of using 40 mg/ml Toluene solvent, the CIE coordinate was (0.345, 0.342) at 20 V.

• Clean Technology
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• v.18 no.4
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• pp.366-372
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• 2012

Three acrylic copolymers containing tris(8-hydroxyquinoline) aluminum (AlQ3) pendant group (25 wt%), acrylateco-HEMA-$AlQ_3$ (25 wt%), were successfully synthesized by free radical polymerization from acrylates [methyl methacrylate (MMA), acrylonitrile (AN) or 2-hydroxyethyl methacrylate (HEMA)] with HEMA functionalized with AlQ3 pendant groups (HEMA-p-$AlQ_3$). The glass transition temperatures ($T_g$) of MMA-co-HEMA-p-$AlQ_3$ (copolymer 1), AN-co-HEMA-p-$AlQ_3$ (copolymer 2) and HEMA-co-HEMA-p-$AlQ_3$ (copolymer 3) were found to be 158, 150 and $126^{\circ}C$, respectively. They have good thermal stability: a very desirable feature for the stability of OLEDs. Their solubility, thermal properties, UV-visible absorption and photoluminescence behaviors were investigated. They were found to be soluble in various organic solvents such as tetrahydrofuran (THF), dimethylformamide (DMF), toluene and chloroform. It was also found that the UV-visible absorption and photoluminescence behaviors of these copolymers were similar to those of pristine $AlQ_3$. Green organic light-emitting diodes (OLEDs) have also been fabricated using these copolymers as light emission/electron transport components obtained easily by spin coating, and their current density voltage (J-V) curves were compared. The OLED device of the copolymer 3 had the lowest turn-on voltage of about 2 V compared to other copolymer types devices.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.160-165
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• 2013

In order to express the natural color in organic light emitting diode(OLED), red, green, and blue luminescent materials are needed. While lots of red and green emitters are searched actively, not many useful blue emitters are found yet. It is due to the high energy gap for the blue emission. This research is about a synthesis of the blue emitting compound with high emission efficiency and thermal stability, which starts with carbazole and anthracene. Carbazole with bulky substituent, tert-butyl group, is connected directly to electroluminescent and thermally stable anthracene. The distance between the hole transporting group and the electron transporting group are studied for the relevance to the luminescence.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1437-1439
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• 2007

We fabricated white organic light emitting device (WOLED) with the layered fluorescent blue material and phosphorescent green/red dye-doped materials. Addition of the non-doped phosphorescent host material between the fluorescent and phosphorescent light emitting layers provided the result of broadband white spectrum, with improved balance, higher efficiency, and lower power consumption. In our devices, there was no need of exciton-blocking layer between the each emission layer for the further confinement of the diffusion of excitons.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.1019-1022
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• 2007

High efficiency in Phosphorescent Organic lightemitting diodes using carbazole type exciton blocking layer were investigated and detailed mechanism for light emission process was studied. Efficiency of green PHOLEDs was enhanced by a factor 3.7.

• 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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.827-834
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• 2010

We have performed numerical simulations of the electrical characteristics for multi-layer organic light emitting diode devices with doped emitting layer using a commercial simulation program. In this paper, the basic structure consists of the ITO/NPB/$Alq_3$:C545T(%)/$Alq_3$/LiF/Al, four devices that were composed of $Alq_3$ as the host and C545T as the green dopant with different concentration, were studied. As the result, the variations of the doping concentration rate of C545T have a effect on the voltage-current density characteristics. The voltage-current characteristics are quite consistent with the results which were experimentally determined in a previous reference paper. In addition, the voltage-luminance characteristics were greatly improved, and the luminous efficiency was improved three times. In order to analyze these driving mechanism, we have investigated the distribution of electric field, charge density of the carriers, and recombination rates in the inner of the OLED devices.