• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2609-2615
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• 2013

A series of fluorene-carbazole copolymers containing the pendant phosphor chromophore $Ir(absn)_2(acac)$ (absn: 2-(1-naphthyl)benzothiazole; acac: acetylacetone) were designed and synthesized via Yamamoto coupling. In the film state, these copolymers exhibited absorption and emission peaks at approximately 389 and 426 nm, respectively, which originated from the fluorene backbone. However, in electroluminescent (EL) devices, a significantly red-shifted emission at approximately 611 nm was observed, which was attributed to the pendant iridium(III) complex. Using these copolymers as a single emission layer, polymer light-emitting devices with ITO/PEDOT:PSS/polymer:DNTPD/TmPyPb/LiF/Al configurations exhibited a saturated red emission at 611 nm. The attached iridium(III) complex had a significant effect on the EL performance. A maximum luminous efficiency of 0.85 cd/A, maximum external quantum efficiency of 0.77, maximum power efficiency of 0.48 lm/W, and maximum luminance of 883 $cd/m^2$ were achieved from a device fabricated with the copolymer containing the iridium(III) complex in a 2% molar ratio.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.1
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• pp.29-35
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• 2000

Luminescent characteristics of SrS:Cu,X TFeL devices fabricated by electron-beam deposition system were studied. The SrS powders were used as the host materials and Cu, $CuF_2,\;Cu_2S$ or CuCl powders were added as the luminescent center. The emission spectra of the SrS:Cu,X TFEL devices strongly depended on coactivators. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:$Cu_2S$ TFEL device were 1443 cd/$m^2$ and 2.44 lm/w, respectively. Green color was observed from this TFEL device. The luminous efficiency of SrS:$Cu_2S$ TFEL device was higher than that of ZnS:Tb TFEL device, and it also could be good green phosphors for TFEL devices. The luminance($L_{40}$) and efficiency(${\eta}_{20}$) of SrS:CuCl TFEL device were 262 cd/$m^2$ and 0.26 lm/w, respectively. Blue color was emitted from this TFEL device.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.124-133
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• 2017

In the current lighting market, LEDs that have a high luminous efficiency, a long life and consume less power have emerged as next generation lighting. Owing to various designs and sizes of LEDs, the production process of existing LEDs involves many tasks that require manual labor; hence, the assembly of LEDs necessitates manpower. Because of the use of manpower, the production costs of LEDs increases and production efficiency decreases. Recently, the assembly parts of LEDs have been standardized for minimizing manual labor, and an LED is developed as an LED panel. The automatic assembly system produces LED convergent lighting by assembling two LED panels and one diffusion cover. To increase the production efficiency of the LED convergent lighting module, it is important that the development of a feeder can continuously supply the LED panels is required, and whose design has sufficient stability. The automatic assembly system of the LED convergent lighting module consists of two feeders, which convey LED panels and diffusion covers to a main conveyor, which assembles the lifted panels and covers. In this study, structural analysis and fatigue life for forced loads on the conveyer line of the feeder in the process of lifting LED panels and diffusion covers of each feeder, is analyzed. In addition, the drive of the belt constituting the conveyor line of each feeder is simulated, and the dynamic characteristics of the belt is analyzed using the virtual engineering method.

• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.244-250
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• 2013

We investigated green phosphorescent organic light-emitting diodes (PHOLEDs) with charge control layer (CCL) to produce high efficiency. The CCL and host material which was 4,4,N,N'-dicarbazolebiphenyl (CBP) of bipolar property can control the carrier movement in emitting layer (EML). The performance improvement by the insertion of CCL was realized to the well confined exciton and the reduced triplet exciton quenching effect in EML. Five types of devices (Device A, B, C, D, and E) were fabricated following the thickness of CCL within EML. The properties of device D using optimized thickness of CCL showed external quantum efficiency of 16.22% and luminous efficiency of 55.76 cd/A, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.781-783
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• 2009

We achieved high efficiency and long lifetime in small-molecule organic light-emitting diodes using a blend of polyaniline-based conducting polymer and a perfluorinated ionomer as a hole injection layer (HIL). The HIL formed by single spin coating greatly enhanced the surface work function and thus the hole injection from the anode, which resulted in great improvement in device luminous efficiency. We find that the solution processed HIL outperforms the conventional vacuum-deposited small molecule HIL in terms of the device performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.750-754
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• 2011

In this research, the electric characteristic of organic light-emitting diodes(OLEDs) was studied depending on thickness of amorphous fluoropolymer(Teflon-AF) which is the material of hole injection layer to improve electric characteristic of OLEDs. Sample composition was fabricated in double layer. The basic structure was fabricated by ITO/tris(8-hydroxyquinoline) aluminum (Alq3)/Al and the 2 layer was fabricated by ITO/2,2-Bistrifluoromethyl-4,5-Difluoro-1,3-Dioxole(Teflon-AF)/tris(8-hydro xyquinoline) aluminum (Alq3)/Al. The experiment was carried with variation of thickness of Teflon-AF at 1.0, 2.0, 2.5, 3.0 nm. The result showed when Teflon-AF thickness was 2.5 nm, the electric and optical characteristic were well performed. Moreover, when it was compared with Teflon-AF without materials, it was improved 15.1 times more on luminance, 12.7 times more on luminous efficiency and 12.1 times more on external quantum efficiency. Therefore, OLEDs element with optimum hole injection layer reduced energy barrier and driving voltage, and confirmed that it improved efficiency widely.

• Journal of Adhesion and Interface
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• v.23 no.2
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• pp.39-43
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• 2022

In optoelectronic devices including displays and solar cells that convert electricity into light or light into electricity, it is important to control optical behavior of light to improve device efficiency. Specifically, the control of internal emitting light in the OLEDs can induce more light to go out, improving luminous efficiency. In addition, the control of optical behavior of incident light in solar cells can increase optical path in the light absorption layer, increasing power-conversion efficiency. In this study, we generated wrinkles as a physical structure to control optical behavior of light and independently controlled their wavelength and height by changing stress relaxation time. To explore the effect of wavelength and height on optical behavior, we conducted UV/Vis spectroscopy analysis of wrinkles with various heights at a constant wavelength or various wavelengths at a comparable height, figuring out a wrinkle with high aspect ratio has more dispersive light and less straight light. It indicates that high aspect ratio is required to change the optical behavior and increase the optical path.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.636-639
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• 2004

We have synthesized a $Eu^{2{\cdot}}$ -activated $Sr_3MgSi_2O_8$ blue phosphor and $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$ yellow phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED chip. Three distinct emission bands from the GaN-based LED and the ($Sr_3MgSi_2O_8$:Eu + $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$:Eu) phosphor are clearly observed at 405nm, 455 nm and at around 540 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based ($Sr_3MgSi_2O_8$:Eu + $Ba^{2{\cdot}}$ co-doped $Sr_2SiO_4$:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.515-517
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• 2004

The laser absorption spectroscopy has been used for measuresurement of the xenon atoms in the resonant $1S_4$ and metastable $1S_5$ states in coplanar AC PDP. For the purpose of improving VUV luminous efficiency and optimization of PDP cells, it is important to study behavior of excited Xe atoms in a micro-discharge cell of a coplanar AC-PDP. We measured the xenon excited density of $1S_5$ and $1S_4$ state under mixture gas of Ne-Xe(10%) with gas pressure of 350 Torr and sustaining gap distance of 150 um.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.688-691
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• 2004

In this study, we synthesized a new red emitting material of a Red225 doped into $Alq_3$ (tris(8-quinolinolato)aluminum (III)) and fabricated white organic light-emitting diodes (OLEDs) with a simple device structure. With a blue emitting material of DPVBi (4,4'-bis(2,2'-diphenylvinyl)1,1'-biphenyl) that can transfer effectively both a hole and an electron, OLEDs with a narrow emission layer could be possible without a hole-blocking layer. Consequently, the driving voltage and stability of devices have been improved. The devices show the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.36, 0.35) at luminance of 2000 cd/$m^2$. The luminous efficiency is about 3.5 cd/A, luminance is about 12000 cd/$m^2$ and current density is about 350 mA/$cm^2$ at 12 V, respectively.