• Journal of the Semiconductor & Display Technology
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• v.5 no.3 s.16
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• pp.1-4
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• 2006

White-light-emitting ZnS:Mn, Cu, Cl phosphors with spherical shape and the size of $20\;{\mu}m$ are successfully synthesized. They have the double phases of cubic and hexagonal structures. They are applied to electroluminescent (EL) devices by silk screen method with the following structure: $electrode/BaTiO_3$ insulator layer ($50{\sim}60\;{\mu}m$)/ ZnS:Mn, Cu, Cl phosphor layer ($30{\sim}50\;{\mu}m$)/ITO glass. The EL devices are driven with the voltage of 100 V and the frequency of 400 Hz. The EL devices show the three emission peaks. The blue and green emission bands are originated from $CICu^{2+}$ transition and $ClCu^+$ transition, respectively. The yellow emission band results from $^4T^6A$ transition of $Mn^{2+}$ ion. As an increase of Cu concentrations, the blue and green emission intensities decrease whereas the yellow emission intensity increases; the quality becomes warm white. It is due to the energy transfer from the blue and green bands to the yellow band.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.353-356
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• 2012

We present new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of the data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue (${\sim}0.44{\mu}m$) and red (${\sim}0.64{\mu}m$) bands. Accurate starlight subtraction was achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with the thermal $100{\mu}m$ brightness, whilst the other shows a constant level in the lowest $100{\mu}m$ brightness region. The presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has an extragalactic origin (i.e., the COB). The derived COB brightness is ($(1.8{\pm}0.9){\times}10^{-9}$ and $(1.2{\pm}0.9){\times}10^{-9}\;erg\;s^{-1}\;cm^{-2}\;sr^{-1}\;{\AA}^{-1}$ in the blue and red spectral regions, respectively, or $7.9{\pm}4.0$ and $7.7{\pm}5.8\;nW\;m^{-2}\;sr^{-1}$. Based on a comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations. There seems to be little room for contributions from other populations including "first stars" at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL)-scattered starlight by the interstellar dust. We derive the mean DGL-to-$100{\mu}m$ brightness ratios of $2.1{\times}10^{-3}$ and $4.6{\times}10^{-3}$ at the two bands, which are roughly consistent with previous observations toward denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1202-1206
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• 2004

Novel naphthyl-containing biphenyl analogues were prepared by Suzki reaction for the chemiluminescent blue fluorophores. UV-Vis absorption, photoluminescence, chemiluminescence and CIE chromaticities were measured. The fluorophores displayed blue photoluminescence in solution with a maximum intensity around 378-415 nm. Sodium salicylate-catalyzed reaction of them with bis(2 carbopentyloxy-3,5,6-trichlorophenyl)-oxalate with hydrogen peroxide provided a strong chemiluminescent red light emission with wavelengths of 398-427 nm; these were similar to the photoluminescent spectra. The chemiluminescent intensity decayed exponentially and the glow of chemiluminescence, which was visible with naked eyes, was maintained for more than 4 h.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.277-278
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• 2009

We have studied an angular dependence of emission pattern of top-emssion organic light-emitting diodes (TEOLED). Device structure is Al(100nm)/TPD(40nm)/$Alq_3$(60nm)/LiF(0.5nm)/Al(2nm)/Ag(30nm). N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) and tris-(8-hydroxyquinoline) aluminium ($Alq_3$)were used as a hole transport layer and emission layer, respectively. Organic layers and cathode were thermally evaporated at $2\times10^{-5}$torr. The evaporation rate of the organic material was maintained to be $1.5\sim2.0{\AA}/s$, and that of metal layer to be $0.5\sim5{\AA}/s$. A transmittance of a cathode electrode(Al/Ag) in visible region is about 25~30%. In order to measure view-angle dependent intensity, electroluminenscence spectra of the device at each angle were integrated. Angle dependent emission spectra of the device do not show blue shift. Emission intensity of the device that the going straight characteristic is stronger the bottom-emission organic light-emitting diodes is shown.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.21-21
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• 2003

To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.91-94
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• 2004

We report on the opto-electronic properties of red, green, and blue poly (fluorene) co-polymer light-emitting devices (PLEDs) fabricated on a flexible plastic substrate. The plastic substrate used has a multi-layer structure with water vapor and oxygen transmission rates of less than $10^{-5}$ g/$cm^2$-day-atm and $10^{-7}$ cc/$cm^2$-day-atm, respectively. We obtained a wide range of color gamut and a maximum emission efficiency of 0.7, 10, and 1.7 cd/A for red, green, and blue PLEDs, respectively. Finally, a simple equivalent circuit model is proposed to simulate PLED current density-voltage characteristics.

• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.258-262
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• 2013

Poly(2,3-naphthalenevinylene-alt-N-ethylhexyl-3,6-carbazolevinylene), 2,3-PNCPV, poly(2,6-naphthalene vinylenealt- N-ethylhexyl-3,6-carbazolevinylene), 2,6-PNCPV, and poly(1,4-naphthalenevinylene-alt-N-ethylhexyl-3,6- carbazolevinylene), 1,4-PNCPV were synthesized through the Wittig polycondensation reaction. The conjugation lengths of the polymers were controlled by differently linked naphthalenes in the polymer main chain. The resulting polymers were completely soluble in common organic solvents, and exhibited good thermal stability at up to $400^{\circ}C$. The synthesized polymers showed UV-visible absorbance and photoluminescence (PL) in the ranges of 357-374 nm and 487-538 nm, respectively. The carbazole and 2,3-linked naphthalene containing 2,3-PNCPV showed a blue PL peak at 487 nm. A single-layer light-emitting diode was fabricated with an ITO/polymer/Al configuration. The electroluminescence (EL) emission of 2,3-PNCPV was shown at 483 nm.

• Journal of Information Display
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• v.6 no.1
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• pp.33-36
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• 2005

To obtain various colors from the blue emitting poly(fluorene)s, two different approaches are introduced. One is copolymerization with low band gap comonomers and the other is molecular doping with various dyes. As fast and efficient exciton migration and trapping and/or energy transfer between the chromorphoric segments or doped dyes in conjugated polymers can shift the emission to longer wavelengths, these phenomena can be utilized to obtain various colors from the intrinsically blue light emitting poly(fluorene)s.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.123-124
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• 2000

Three types of conjugated polymer, poly(DFPZ-AV), poly(MEHPV-PV) and poly(BFMP12-BPV), were obtained by Honer-Emmons condensation using potassium tert-butoxide from the synthesized monomers in anhydrous tetrahydrofurane. The Honer-Emmons reaction was found to be a useful synthetic method for the preparing a wide range of EL polymers. The EL devices using poly(DFPZ-AV), poly(MEHPV-PV) and poly(BFMP12-BPV) as light emitting layer gave red, green and blue emission, respectively, which were in close chromaticity with the CIE 1931 NTSC standard.

• Transactions on Electrical and Electronic Materials
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• v.13 no.6
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• pp.317-321
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• 2012

Poly[4,4'(3,3')-biphenylenevinylene-alt-2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene], 4,4'(3,3')-PBPMEH-PPV, and poly[4,4'(3,3')-biphenylenevinylene-alt-N-ethylhexyl-3,6-carbazolevinylene], 4,4'(3,3')-PBPCAR-PPV, of varying effective conjugation lengths, were synthesized by the well-known Wittig condensation polymerization between the appropriate biphenyl diphosphonium salts and dialdehyde monomers such as carbazole or dialkoxyphenyl dialdehyde. The conjugation lengths of the polymers were controlled by biphenyl linkages (4,4' or 3,3'). The resulting polymers were highly soluble in common organic solvents and exhibited good thermal stability up to $300^{\circ}C$. The synthesized polymers showed UV-visible absorbance and photoluminescence (PL) in the ranges of 314-400 nm and 430-507 nm, respectively. Carbazole and 3,3'-biphenyl containing 3,3'-PBPCAR-PPV showed a blue PL peak at 430 nm. A single-layer light-emitting diode was fabricated in a configuration of ITO/polymer/Al. Electroluminescence (EL) emission of 3,3'-PBPCAR-PPV was shown at 455 nm.