• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1432-1435
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• 2005

We report failure mode observed in polymer EL blue devices, relating with life curve. The modes are analyzed by observing compositional and morphological variation using TEM-EDX, STM, and reverse engineering method as destructive ways, and also investigated mobility changes of hole and electron by measuring transient EL as a nondestructive way corresponding to life curve. We believe that the postulated failure modes in polymer EL devices can present right directions to obtain better performance, especially life time, of polymer devices in material and device structural designing points of view.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.6
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• pp.568-573
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• 2006

We have synthesized new blue light emitting random copolymers, poly(9,9'-n-dioctylfluorene-co-perfluorobenzene-1,4-diyl)s (PFFBs), via Ni(0)-mediated coupling reactions. The weight-average molecular weights ($M_w$) of the PFFB copolymers ranged from 9,000 to 15,000. The PFFB copolymers dissolved in common organic solvents such as THF and toluene. The PL emission peaks of the PFFB copolymers were at around 420, 440, and 470 nm. EL devices were fabricated in ITO/PEDOT/polymer/Ca/Al configurations using these polymers. These EL devices were found to exhibit pure blue emission with approximate CIE coordinates of (0.15, 0.11) at $100cd/m^2$. The blue emissions of these devices might be due to the restriction of the polymer chains to aggregation by introducing of the highly electronegative fluorine moieties. The maximum brightnesses of the PFFB copolymer devices ranged from 140 to $3600cd/m^2$ with maximum efficiencies from 0.2 to 0.6 cd/A. The enhanced efficiency of the PFFB (8/2) copolymer device results from the inhibition of excimer formation by the introduction of the electronegative fluorine moieties into the copolymers.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.24-27
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• 1998

Electroluminescence (EL) comes from the light emission obtained by the electrical excitation energy passing through a phosphor layer undo. an applied high electrical field $(10^6 V/cm)$. The preparation of white and blue phosphors and characterizations of light emitting alternating current powder electroluminescent devices (ACPELDs) were investigated. In this work, we fabricated two kinds of ELDs, that is, yellow electroluminescent device (B-ELD), blue electroluminescent device (B-ELD). The basic st.uctures of Y-ELD and B-ELD are ITO (Indium Tin Oxide)/phosphor layer/Insulator layer/Carbon electrode and ITO/Phosphor layer/Insulating layer/carbon electrode, respectively. Another structures of ITO/Phosphor and Insulator mixture layer/Backelectrode are introduced. EL spectra and luminance of two types of ELDs were measured by changing voltage at fixed frequency 0.4kHz, 1.5kHz. Blue and yellow phosphors prepared in this work show $50cd/m^2\;and\;30cd/m^2$ of luminance at 400Hz, 150V.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.149-150
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• 2000

Lead-doped calcium sulfide(CaS:Pb) thin film electroluminescent devices were deposited using atomic layer deposition(ALD). CaS:Pb is a very promising blue phosphor showing very high luminance and the color coordinate close to the blue of cathode ray tube. The luminance, $L_{25}$, of CaS:Pb(1.6 mol.%) EL device was higher than 80 $cd/cm^2$ at a driving frequency of 60Hz. The color coordinates of blue EL emission of CaS:Pb deposited by ALD are consistent with the Pb concentration ranging from approximately 0.5 to 3 mol.%.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.316-323
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• 2003

Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the ${\pi}$-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 $cd/m^2$ at 12V, current density, 575 $mA/m^2$ was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.

• Journal of Information Display
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• v.8 no.2
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• pp.20-24
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• 2007

Efficient white organic light-emitting diodes are fabricated with the blue and red electroluminescent (EL) units electrically connected in a stacked tandem structure by using a transparent doped organic p/n junction. The blue and red EL units consist of the light-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi) and 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j] quinolizin-8-yl)vinyl]-4H-pyran) (DCM2) doped tris(8-hydroxyquinoline) aluminum $(Alq_3)$, respectively. The organic p-n junction consists of ${\alpha}-NPD$ doped with $FeCl_3$ (15 % by weight ratio) and $Alq_3$ doped with Li (10 %). The EL spectra exhibit two peaks at 448 and 606 nm, resulting in white light-emission with the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.36, 0.24). The tandem device shows the quantum efficiency of about 2.2 % at a luminance of 100 $cd/m^2$, higher than individual blue and red EL devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.648-651
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• 2001

We studied about luminance characteristics of blue organic electroluminecent device as thickness ratio. The device is fabricated TPD(N,N'-dyphenyl-N-N'-bis(3-methyphenyl) -1,1'-biphenyl-4,4'-diamine) as hole transport layer and Butyl -PBD(1,1,4,4-Tetraphenyl-1,3-butadiene) as emission layer and electron transport layer. Total thickness is 1000${\AA}$ as HTL and ETL, each devices has 500${\AA}$:500${\AA}$. 400${\AA}$:600${\AA}$ and 600${\AA}$:400${\AA}$ of TPD : Butyl-PBD. We obtained the maximum brightness about 175cd/㎡ 500${\AA}$: 500${\AA}$ thickness devices as HTL:ETL

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.411-412
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• 2007

EL (electro luminescent) is generally studied as a large size plane light emitting device and flexible light source because of it's simple manufacturing process. In this experiment, we manufactured flexible white emitting light source using Ni-foil with blue phosphor and color change materials. With increasing the thickness of color change material, the luminance of white emission is increased and the color coordinate of white color was shifted to pure white of (0.317,0.328) by strong emission of color change materials excited by blue excitation spectra. Also the luminance level was 30% higher in white emitting light device than blue only light source.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.265-268
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• 2004

We have developed a highly efficient and stable blue organic electroluminescent device (OLED) based on the blue fluorescent p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) dopant in a morphologically stable high-bandgap host material, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN), which achieved an EL efficiency of 9.7 cd/A and 5.5 lm/W at 20 mA/$cm^2$ and 5.7 V with a Commission Internationale d'Eclairage coordinates of(x = 0.16, y = 0.32). This sky blue device which could also alleviate the problematic current induced quenching at high current achieved a half-decay lifetime ($t_{1\;2}$) of 46,000 h at an initial brightness of 100 cd/$m^2$.

• Journal of Information Display
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• v.8 no.1
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• pp.10-13
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• 2007

We synthesized new blue and bluish green emitting materials by using fully substituted ethylene moieties. Multi-layered EL devices were fabricated with synthesized materials and evaluated in terms of emission color and luminescence efficiency. TBBPE[EML 2] device showed bluish-green CIE value of (0.236, 0.412) and 5.02cd/A at $10mA/cm^2$. BPBBPE[EML 3] device also showed sky-blue CIE value of(0.218, 0.355) and 2.31cd/A at $l0mA/cm^2$.