• Journal of the Korean Applied Science and Technology
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• v.19 no.3
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• pp.174-180
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• 2002

In recent days, the study of a new phosphorescent phosphor has been performed in order to overcome the defect of sulfide phosphor and increase the brightness and long after-glow characteristic of phosphorescent phosphor. Particularly, sulfide phosphor usually used is so chemically unstable that the study of oxide phosphors are processing. $Eu^{2+}$, $Nd^{3+}$ doped Ba-Al-O phosphors sintered at $600{\sim}1500^{\circ}C$ for 2hours had the PL emission spectrum and after-glow over $1200^{\circ}C$. In this system, as the mole concentration of alumina increases, emission bands of phosphors moved from 500nm to 380nm. The optimum concentration of flux was 5wt% and after-glow characteristics of phosphors were found at the host material molar ratio ($BaCO_{3}:Al_{2}O_{3}$), 1:1 and 1:3.

• ETRI Journal
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• v.34 no.5
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• pp.690-695
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• 2012

We investigate the light-emitting performances of blue phosphorescent organic light-emitting diodes (PHOLEDs) with three different electron injection and transport materials, that is, bathocuproine(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline) (Bphen), 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (Tm3PyPB), and 2,6-bis(3-(carbazol-9-yl)phenyl)pyridine (26DCzPPy), which are partially doped with cesium metal. We find that the device characteristics are very dependent on the nature of the introduced electron injection layer (EIL) and electron transporting layer (ETL). When the appropriate EIL and ETL are combined, the peak external quantum efficiency and peak power efficiency improve up to 20.7% and 45.6 lm/W, respectively. Moreover, this blue PHOLED even maintains high external quantum efficiency of 19.6% and 16.9% at a luminance of $1,000cd/m^2$ and $10,000cd/m^2$, respectively.

• Korean Journal of Materials Research
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• v.19 no.5
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• pp.240-244
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• 2009

Simple and high efficiency green phosphorescent devices using an intermixed double host of 4, 4', 4"-tris(N-carbazolyl) triphenylamine [TCTA], 1, 3, 5-tris (N-phenylbenzimiazole-2-yl) benzene [TPBI], phosphorescent dye of tris(2-phenylpyridine)iridium(III) [$Ir(ppy)_3$], and selective doping in the TPBI region were fabricated, and their electro luminescent characteristics were evaluated. In the device fabrication, layers of $70{\AA}$-TCTA/$90{\AA}$-$TCTA_[0.5}TPBI_{0.5}$/$90{\AA}$-TPBI doped with $Ir(ppy)_3$ of 8% and an undoped layer of $50{\AA}$-TPBI were successively deposited to form an emission region, and SFC137 [proprietary electron transporting material] with three different thicknesses of $300{\AA}$, $500{\AA}$, and $700{\AA}$ were used as an electron transport layer. The device with $500{\AA}$-SFC137 showed the luminance of $48,300\;cd/m^2$ at an applied voltage of 10 V, and a maximum current efficiency of 57 cd/A under a luminance of $230\;cd/m^2$. The peak wavelength in the electroluminescent spectral and color coordinates on the Commission Internationale de I'Eclairage [CIE] chart were 512 nm and (0.31, 0.62), respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.11
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• pp.704-710
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• 2015

We studied white organic light-emitting diodes using blue fluorescent and red phosphorescent materials. White single OLEDs were fabricated using SH-1 : BD-2 (3 vol.%) and CBP : $Ir(mphmq)_2(acac)$ (2 vol.%) as emitting layer (EML). The white single OLED using SH-1 : BD-2 (3 vol.% 8 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 22 nm) as emitting layer showed maximum current efficiency of 8.8 cd/A, Commission Internationale de l'Eclairage (CIE) coordinates of (0.403, 0.351) at $1,000cd/m^2$, and variation of CIE coordinates with ($0.402{\pm}0.012$, $0.35{\pm}0.002$) from 500 to $3,000cd/m^2$. The white tandem OLED using SH-1 : BD-2 (3 vol.% 12 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 18 nm) showed maximum efficiency of 19.6 cd/A, CIE coordinates of (0.354, 0.365) at $1,000cd/m^2$, and variation of CIE coordinates with ($0.356{\pm}0.016$, $0.364{\pm}0.002$) from 500 to $3,000cd/m^2$. Maximum current efficiency of the white tandem OLED was more twice as high as the single OLED. Our findings suggest that tandem OLED was possible to produce improved efficiency and excellent color stability.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.503-505
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• 2008

A host material containing tetraphenylsilane, 9-(4-triphenylsilanyl-(1,1'4,1")-terphenyl-4"-yl)-9H-cabazole (TSTC), was synthesized for green phosphorescent organic emitting diodes. $Ir(ppy)_3$ based OLEDs using TSTC host and DTBT (2,4-diphenyl-6-(4'yl)-1,3,5-triazine) hole blocking layer (HBL) showed the maximum external quantum efficiency of 19.8 %, the power efficiency of 59.4 lm and high operational stability with a half lifetime of 160,000 h at an initial luminance of $100\;cd/m^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.402-403
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• 2007

High-efficiency white organic light-emitting diodes (WOLEDs) were fabricated with two emissive layers and a spacer was sandwiched between two phosphorescent dyes which were, bis(3,5-Difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (FIrpic) as the blue emission and bis(5-acetyl-2-phenylpyridinato-N,C2') acetylacetonate $((acppy)_2Ir(acac))$ as the red emission. This spacer effectively prevented a triple-triple energy transfer between the two phosphorescent emissive layers with blue and red emission that was showed a improved lifetime. The white device showed Commission Internationale De L'Eclairage $(CIE_{x,y})$ coordinates of (0.33, 0.42) at $22400\;cd/m^2$, a maximum luminance of $27300\;cd/m^2\;at\;0.388\;mA/cm^2$, and a maximum luminous efficiency of 26.9 cd/A.

• YAKHAK HOEJI
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• v.7 no.1
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• pp.26-29
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• 1963

Three systems such as CaS, BaS and ZnS are used as ground materials and transition elements such as Bi, Cu, Ag and Ni are used as activators to preared phosphorescent materials of strong after-grow intensity. These three systems in which we have 31 kinds of different composition samples are heated at given temperatures in the electrical furnace and are cooled in the air in order to crystallize them. In the case of BaS system, the mixture of CaO and purified S is better than the other kinds of calcium compound as the ground materials to crystallize phosphors. In BaS system, the mixture of BaCO$_{3}$ and purified S, in ZnS system ZnS respectively is the most proper ground material to prepare such a strong after-grow intensified phosphors. In a given range, the higher in temperature and the longer time of heating, the better phosphors we obtain.

• Journal of the Korean Applied Science and Technology
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• v.25 no.2
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• pp.265-268
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• 2008

Among the efforts to increase the efficiency of organic light-emitting device (OLED), there is a way: doping phosphorescent materials. As a phosphorescent material, complexes of heavy transition metal, platinum, were synthesized. $Cl^-$ ion and phenyl group were used as ancillary ligands with 2-(2-pyridyl)benzimidazole (pbi) as a chromophore. The complexes were analysed by FAB-mass spectrometer and absorption and emission spectra were obtained. A phenyl group was able to shift the emission band of the complex even if it's not a chromorphore.

• Transactions on Electrical and Electronic Materials
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• v.12 no.2
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• pp.80-83
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• 2011

We have fabricated phosphorescent white organic light-emitting devices (WOLEDs) with a spin-coated poly(Nvinylcarbazole) [PVK] host layer. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,$C^{2'}$]picolinate (FIrpic), tris(2-phenylpyridine)iridium(III) [$Ir(ppy)_3$], and tris(2-phenyl-1-quinoline)iridium(III) [$Ir(phq)_3$], were used as the blue, green, and red guest materials, respectively. The PVK was mixed with FIrpic, $Ir(ppy)_3$, and $Ir(phq)_3$ molecules in a chlorobenzene solution and spin-coated in order to prepare the emission layer; 3-(4-biphenylyl)-4-phenyl-5-(4-tertbutylphenyl)-1,2,4-triazole (TAZ) was used as an electron transport material. The resultant device structure was ITO/PVK:FIrpic:$Ir(ppy)_3:Ir(phq)_3$/TAZ/LiF/Al. The electroluminescence, efficiency, and electrical conduction characteristics of the WOLEDs based on the doped PVK host layer were investigated. The maximum current efficiency of the three wavelength WOLED with the doped PVK host was 19.2 cd/A.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1039-1044
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• 2009

Red color OLED has been fabricated by the doping method apply to CBP using co-evaporation, GDI4349 of phosphorescent dopant, and rubrene of fluorescent dopant. The OLED structure are multi-layer of ITO(150 nm)/ELM_HIL(50 nm)/ELM_HTL(30 nm)/CBP : Rubrene, GDI4349 (30 nm)/BAlq (30 nm)/LiF(0.7 nm)/Al (100 nm). Accomplished best result at 3 vol.% of rubrene when the OLEDs were made of 1, 3, 5, 7, 9 vol.% doped rubrene. The highest efficiency of 7.2 cd/A was resulted at 8 vol.% of GDI4349 when the OLEDs were made among 5, 8, 11, 14 vol.% of GDI4349. Obviously, the best concentration of rubrene at 3 vol.% and changing GDI4349 concentration to 5, 8, 11, 14 vol.% OLED dramatically enhanced characteristic of resulted 10.7 cd/A at 8 vol.% of GDI4349. This result would understand to analyse as the emission efficiency increases by energy transport efficiency increase using GDI4349 energy transfer when rubrene absorbs the energy from CBP of fluorescences host.