• 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.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.970-973
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• 2003

A new class of soluble PPV derivatives containing dimethyldodecylsilylphenyl unit as a pendant was synthesized by Gilch polymerization method. The resulting electroluminescent (EL) polymers showed good solubility, good film-forming ability onto the ITO substrate, and exhibited an amorphous morphology due to dimethyldodecylsilylphenyl branched group linked to the polymer backbone. The weight average molecular weights and polydispersities of the present EL polymers were in the range of 8.0-80.0 x $10^{4}$ and 2.67-7.80, respectively. The resulting EL polymers revealed a high thermal stability of up to $355-410^{\circ}C$. Their glass transition temperatures were in the range of $104-251^{\circ}C$. The emission colors could be tuned from green to orange-red colors by changing the MEH-PPV contents in copolymer systems. The turn-on voltages of the EL polymers were in the range of 1.8-4.0 V.

• Journal of Information Display
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• v.2 no.3
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• pp.1-5
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• 2001

The effect of doping on the energy transfer and charge carrier trapping processes has been studied in organic light-emitting diodes (OLEDs) doped with a fluorescent laser dye. The devices consisted of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1-biphenyl-4,4'-diamine (TPD) as a hole transporting layer, tris(8-hydroxyquinoline) aluminum ($Alq_3$) as the host, and a fluorescent dye, 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1 H,5H-benzo[i,j]quinolizin-8-yl) vinyl]-4H-pyran) (DCM2) as the dopant. Temperature dependence of the current-voltage-luminescence (I-V-L) characteristics, the electroluminescence (EL) and photoluminescence (PL) spectra are studied in the temperature ranging between 15 K and 300 K. The emission from DCM2 was seen to be much stronger compared with the emission from $Alq_3$, indicative of efficient energy transfer from $Alq_3$ to DCM2. In addition, the EL emission from DCM2 increasd with increasing temperature while the emission from the host $Alq_3$ decreased. The result indicates that direct charge carrier trapping becomes efficient with increasing temperature. The EL emission from DCM2 shows a slightly sublinear dependence on the current density, implying the enhanced quenching of excitons at high current densities due to the exciton-exciton annihilation.

• Journal of Information Display
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• v.5 no.4
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• pp.12-17
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• 2004

A series of statistical random copolymers of dioctylfluorene (DOF) and 3,4-ethylenedioxythiophene (EDOT) were synthesized by Ni (0) mediated polymerization and their light-emitting properties were compared with poly (9,9-di-n-octylfluorene) (PDOF). The synthesized polymers were characterized using UV-vis spectroscopy, TGA, photoluminescence (PL) & electroluminescence (EL) spectroscopy and by conducting molecular weight studies. The resulting polymers were found to be thermally stable and readily soluble in organic solvents. The UV-visible absorption and PL emission spectra of the copolymers were gradually red-shifted as the fraction of EDOT in copolymers increased. Light-emitting devices were fabricated in an ITO (indium-tin oxide)/PEDOT/polymer/Ca/Al configuration. Interestingly, the EL spectra of these devices were similar to the PL spectra of the corresponding polymer film. However, the EL devices constructed from the copolymer showed more than 10 times higher efficiency level than the devices constructed from the PDOF homopolymer. This higher efficiency is possibly the result of better charge carrier balance in the copolymer systems due to the lower HOMO levels of the copolymers in comparison to that of PDOF homopolymer.

• Korean Journal of Optics and Photonics
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• v.13 no.2
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• pp.128-133
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• 2002

In a recent effort to develop polymer light-emitting diodes (LEDs) as promising flat panel display components, measurements of reliable absolute photoluminescence (PL) and electroluminescence (EL) efficiency for polymer materials are required. In this work, we performed the measurement of PL and EL efficiency of luminescent polymers using an integrating sphere technique. The external PL efficiency of MEH-PPV was estimated to be 8 ($\pm$2)% together with the value of 0.02 1m/W for the external EL efficiency. This PL efficiency is in good agreement with published values, indicating that our PL efficiency measurements are somewhat legitimate. We believe this study might contribute to the research and development of organic materials for optoelectronic devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1353-1356
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• 2004

In recent year, OLED(organic light emitted display) is used as the next generation device of FPD. OLED have been replacing the flat panel display device such as LCD, STN-LCD and TFT because this device is more efficient, economic and simple than those FPD devices, and this need not backlight system for visualization. The performance and efficiency of OLED is related with surface defect of ITO coated glass substrate. The typical surface defect of glass substrate is nonuniformity and bad surface roughness. ITO coated glass substrate is destroied for inspection about surface roughness and non-uniformity. Generally detection of the defects in the surface for ITO coated glass substrate is dependent on operator's experience. In this research, relationship between working parameter and surface non-uniformity is studied using regression analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.249-252
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• 1997

Electroluminescence(EL) devices based on organic thin layers have attracted lot of interests because of their possible application as large-area display-emitting display. One of the problems of such devices is lifetime of the cell, where the degradation of the cell is partially due to the crystalliyzation of organic layers. In large part, this problem can be solved by using a multilayer device structure prepared by vapor deposition technique. In this study, blue light-emitting multilayer organic electroluminescence devices were fabricated vsing Poly (9-vinylcarbaEole) (PVK) and 2- (4-tert-butylphenyl)-5-(4$^{#}$-bis-phenyl) 1,3,4-oxadiazole (PBO) as hole trasport and electron transport material, respectively, where trim(8-hyd roxyquinolinate) aluminum (Al $q_3$) was used as a luminescenct material. A cell structure of glass sub- strate/indume-tin-oxide(ITO)/PCK/Al $q_3$/PBD/Mg:In was employed. Blue emission peak at 510nm was observed with this cell structure.e.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.776-778
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• 1998

Electrical and optical characteristics of Powder type EL display(P-ELD) in this study are described, In experimental results of V-J, current are increased with increasing the frequency and voltage. Luminance was increased with frequency. This is due to the positive space charge formed to cathode region. Lumiance at 150V, 20 kHz has $840\;cd/m^2$. This tendency is due to the decrease of capacitive reactance in insulator layer. Uniformity of P-ELD shows 97%. CIE chromaticity with increasing frequency are shifted toward blue color. It can be explained in tenn of the difference of recombination energy.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.974-977
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• 2003

A new series of statistical alternating EL copolymer, poly[bis{2-(4-phenylenevinylene)-2-cyanoethenyl}- 9,9-dihexyl-9H-fluorene-2,7-yl-alt-1,4-phenylene vinylene] (polymer-I) was synthesized by the modified Heck coupling reaction, and their EL characteristics were also investigated. Double layer polymer light-emitting display (PLED) with the configuration of ITO/PEDOT/polymer/Al devices show maximum brightness and luminous efficiency up to 3000 $cd/m^{2}$ at 30 V and 0.07 lm/W at 21 V, respectively.

• Journal of the Semiconductor & Display Technology
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• v.19 no.1
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• pp.49-54
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• 2020

The voltage drop due to the thin cathode film at the large size top emission OLED panel was successfully compensated with making electrical contact between thin cathode and anode auxiliary electrode by 355nm wavelength of laser. It was found that the luminance uniformity dramatically increased from around 15% to more than 80% through this electrical compensation between thin cathode and anode auxiliary electrode. Moreover, the removing process for EL materials on the anode auxiliary electrode process by laser was very reliable and stable. Therefore, it is thought that the EL removal method using laser to make electrical contacts is very appropriate to mass production for such a large size top emission OLEDs to obtain high uniformity of luminance.