• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.549-552
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• 2008

We have developed a novel bipolar host material with both electron and hole transporting characteristics. Since CGH(Cheil Green Host) has some electron transporting characteristics, it shows increased luminance efficiency in device including TCTA and without HBL(hole blocking layer:BAlq). Maximum power efficency of CGH was 27.4lm/W at the device structure ITO/DNTPD(60)/NPB(20)/TCTA(10)/EML(30)/Alq3(20)/LIF(1)/Al. We measured device performance again without HBL. The result of CGH showing 26.0lm/W is outstanding compared to that of CBP showing 19.1lm/W without holeblocking layer. We also measured lifetime and found to be 205hr at 3000nit, that is significant result compared to the life time of CBP device showing 82hr. CGH shows high device performance with holeblocking layer. Moreover, it shows better device performance and life time than those of CBP without holeblocking.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.299-302
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• 1998

Electroluminescent(EL) devices based on organic materials have been of great interest due to their possible applications for large-area flat-panel displays. They are attractive because of multicolor emission low operation voltage. In this study, several Eu complexes such as Eu(TPB)$_3$(Phen) and Eu(TPB)$_3$(Bpy) were synthesized and the photoluminescence(PL) and electroluminescence (EL) characteristics of their thin films were investigated by fabricating the devices having a structure of glass substrate/ITO/TPD/Europium-complexs/Alq$_3$/Al, where aromatic diamine(TPD) was used as an hole transporting and Alq$_3$ was used as an electron transporting materials. It was found that the photoluminescence(PL) and electroluminescence(EL) characteristics of these Europium complexes were dependent upon the ligands coordinated to Europium metal. Details on the explanation of electrical transport phenomena of the structure with I-V characteristics of the OLEDs using the trapped-charge-limited current(TCLC) model will be discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.265-268
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• 1997

Electroluminescent(EL) devices are constructed using multilayer organic thin film. A cell structure of glass substrate/Indium-Tinoxide/TPD as a hole transporting layer/Alq3+Rhodamine 101 perchrolate(Red3) as an emitting layer/Alq3 as an electrron transporting layer/Al as an electrode was employed. Optimal thickness of emitting layer in EL cell was performed from the viewpoint of the electronics properties of emitting layers. The general vapor-deposition method was used to control the thickness of omitting layer in EL devices and electro-optical characteristics were measured. It is clarified that controlling thickness of emitting layer in vapor-deposition film had an effect on the change of carrier injection and EL spectrum. The intensity of red omission with luminance of 81cd/$m^2$ was achived at 11V driving voltage. The surface morphology of emitting layer in EL devices was investigated.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.636-639
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• 2007

We have developed novel bipolar host materials, designed to have both electron transporting and hole transporting abilities, which show significant increase in luminance efficiency and decrease in driving voltage of green phosphorescent OLEDs. In case of the best host material, CheilGH-3, the driving voltage was decreased 27 % at a given constant luminance of $1000cd/m^2$. Also the luminance efficiency was enhanced 44 % and the power efficiency was almost doubled compared to the reference device using CBP as a host.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.315-318
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• 1998

Organic light-emitting diodes(OLEDs) or electroluminescent devices have attracted much attention because of their possible application as large-area light-emitting displays. Their structure was based on employing a multilayer device structure containing an emitting layer and a carrier transporting layer of suitable organic materials. In this study, several Tb complexes such as Tb(ACAC)$_3$(Phen), Tb(ACAC)$_3$(Phen-Cl) and Tb(TPB)$_3$(Phen) were synthesized and the photoluminescence(PL) and electroluminescence (EL) characteristics of their thin films were investigated by fabricating the devices having a structure of anode/HTL/terbium-oomplex/ETL/cathode, where TPD was used as an hole transporting and Alq$_3$ and TAZ-Si were used as an electron transporting materials. It was found that the photoluminescence(PL) and electroluminescence(EL) characteristics of these terbium complexes were dependent upon the ligands coordinated to terbium metal. Details on the explanation of electrical transport phenomena of the structure with I-V characteristics of the OLEDs using the trapped-charge-limited current(TCLC) model will be discussed.

• 한국전기전자재료학회논문지
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• 제24권8호
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• pp.664-668
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• 2011

In this study, we have fabricated the red OLED (organic light emitting diode). The basic device structure is ITO/hole transporting layer, TPD(500 $\AA$)/red emitting layer, Alq3 doped with DCM2:rubrene(20 $\AA$)/electron transporting layer, Alq3(M) (500 $\AA$-M $\AA$)/LiF(15 $\AA$)/Al(1,000 $\AA$). The thickness of electron transporting layer(500 $\AA$-M $\AA$) changed 0, 20, 40, 60 $\AA$. Turn on voltage of the red OLED was 5 V, 6 V, 6.5 V and 7.5 V, respectively with electron transfer layer changed ratio. Luminance of red OLED was 4,504, 1,840, 1,490 and 1,130 cd/$m^2$, respectively. Optimized electron transfer layer position changed ratio of the red OLED was 0 $\AA$.

• 한국응용과학기술학회지
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• 제17권2호
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• pp.120-125
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• 2000

The tfTZ(4,4',4''-trifluoro-triazine) was used as a hole blocking material for the electroluminescent devices(ELDs) in this study. In general, the holes are outnumbered the electrons in hole transport and emitting layers because the hole transport is more efficient in most organic ELDs. The hole blocking layer are expected to control the excess holes to increase the recombination of holes and electrons and to decrease current density. The former study using the 2,4,6-triphenyl-1,3,5-triazine(TTA) as hole blocking layer showed that the TTA did not form stable films with vapor deposition technique. The tfTZ can generate stable evaporated films, moreover the fluorine group can lower the highest occupied molecular orbital(HOMO) level, which produces the energy barrier for the holes. The tfTZ has high electron affinities according to the data by the Cyclic-Voltammety(CV) method, which is developed for the measurement of HOMO and lowest occupied molecular orbital(LUMO) level of organic thin films. The lowered HOMO level is made the tfTZ to be applied for a hole blocking layer in ELDs. We fabricated multilayer ELDs with a structure of ITO/hole blocking layer(HBL)/hole transporting layer(HTL)/emitting layer/electrode. The hole blocking properties of this devices is confirmed from the lowered current density values compared with that without hole blocking layer.

• 한국전기전자재료학회논문지
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• 제18권7호
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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.

• ETRI Journal
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• 제33권1호
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• pp.32-38
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• 2011

We investigated the light-emitting performances of blue phosphorescent organic light-emitting diodes, known as PHOLEDs, by incorporating an N,N'-dicarbazolyl-3,5-benzen interlayer between the hole transporting layer and emitting layer (EML). We found that the effects of the introduced interlayer for triplet exciton confinement and hole/electron balance in the EML were exceptionally dependent on the host materials: 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole, and 4,4'-bis-triphenylsilanyl-biphenyl. When an appropriate interlayer and host material were combined, the peak external quantum efficiency was greatly enhanced by over 21 times from 0.79% to 17.1%. Studies on the recombination zone using a series of host materials were also conducted.

• 한국전기전자재료학회논문지
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• 제31권7호
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• pp.486-489
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• 2018

Solution-processed organic light-emitting diodes (OLEDs) have the advantages of low cost, fast fabrication, and large-area devices. However, most studies on solution-processed OLEDs have mainly focused on solution-processable hole transporting materials or emissive materials. Here, we report fully solution-processed green OLEDs including hole/electron transport layers and emissive layers. The electrical and optical properties of OLEDs based on solution-processed TPBi (2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) as the electron transport layer were investigated with respect to the spin speed and the number of layers. The performance of OLEDs with solution-processed TPBi exhibits a power efficiency of 9.4 lm/W. We believe that the solution-processed electron transport layers can contribute to the development of efficient fully solution-processed multilayered OLEDs.