• Journal of the Semiconductor & Display Technology
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• v.11 no.3
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• pp.33-37
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• 2012

Simple and high efficiency blue organic light-emitting diodes with three organic layers of N, N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolylamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD]/1,1-bis-(di-4-polya-minophenyl)cyclohexane[TAPC]/electron transport material [ET-137] were fabricated and their electroluminescent characteristics were evaluated according to the TAPC thickness variation in a range of $50{\sim}300{\AA}$. Electroluminescence spectra of the devices with structure of DNTPD/TAPC/ET-137 showed all the same central emission wavelengths of 455 nm under an applied voltage of 7V, which were similar with that of the device with ET-137 only. On the other hand, the electroluminescence spectra of the device with structure of DNTPD/ET-137 without TAPC layer showed double emission peaks at the wavelengths of 455 nm and 561 nm under an applied voltage of 7V. In the devices with structure of DNTPD/TAPC/ET-137, single peak blue emission was not maintained in the device with $50{\AA}$-thick TAPC above 8V by the formation of exciplex. In the device with $300{\AA}$-thick TAPC, however, single peak blue emission was maintained until 10 V. According to the thickness increase of TAPC in the fabricated devices, the current density and luminance decreased, but the luminous efficiency and roll-off characteristics were improved.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.98-103
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• 2001

A new application of dirchroic mirror for the improvement of luminance and luminous efficacy in an AC-Plasma Display Panel (PDP) is suggested. Only about half of the Vacuum Ultraviolet (VUV) generated in the reflective PDP cell is used for the excitation of the phosphor. We are suggesting an idea of adopting a dichroic mirror which can reflect the VUV toward the phosphor which otherwise is absorbed by the front panel. The optical constants of the thin films of dirhroic mirror were determined from the photometric measurements through an iteration process of matching calculated and measured values of the reflectance and transmittance in the VUV wavelength region. From these results, we could design such a filter whose high reflection zone is centered at 147nm by a computer simulation accurately. The 147nm VUV is radiated from Xenon 3Pl state which is dominantly used to activate the phosphor in the PDP cell. The dichroic mirror was made with an electronbeam evaporator and its reflectance was measured by a reflectometer. We confirmed the usefulness of the dichroic mirror for the improvement of efficiency with experiments done by test panels. The panel with mirror shows improved luminance and luminous efficacy by 20∼30％.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.752-756
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• 2002

Green-emitting $Zn_2SiO_4:Mn$ phosphors for PDP(Plasma Display Panel) application were synthesized by colloidal seed-assisted spray pyrolysis process. The codoping with $Gd^{3+}/Li^+$, which replaces $Si^{4+}$ site in the willemite structure, was performed to improve the luminous properties of the $Zn_2SiO_4:Mn$ phosphors. The particles prepared by spray pyrolysis process using fumed silica colloidal solution had a spherical shape, small particle size, narrow size distribution, and non-aggregation characteristics. The $Gd^{3+}/Li^+$ codoping amount affected the luminous characteristics of $Zn_2SiO_4:Mn$ phosphors. The codoping with proper amounts of $Gd^{3+}/Li^+$ improved both the photoluminescence efficiency and decay time of $Zn_2SiO_4:Mn$ phosphor particles. In spray pyrolysis, the post-treatment temperature is another factor controlling the luminous performance of $Zn_2SiO_4:Mn$ phosphors. The $Zn_{1.9}SiO_4:Mn_{0.1}$ phosphor particles containing 0.1 mol% $Gd^{3+}/Li^+$ co-dopant had a 5% higher PL intensity than the commercial product and 5.7 ms decay time after post-treatment at $1,145^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.389-396
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• 2010

In this paper, we reported the synthesis and electroluminescent properties of blue fluorescent styrylamine derivatives end-capped with a diphenylvinyl group. A new series of styrylamine derivatives have been synthesized via the Horner-Wadsworth-Emmons reaction. To explore electroluminescent properties of these molecules, multilayer organic lighte-mitting devices with the configuration of ITO/NPB/1-5 doped in MADN/Bphen/Liq/Al were fabricated. All devices exhibited blue emissions with good EL performances. Among those reported herein, the device using dopant 5 exhibited a maximum luminance of $24,000\;cd/m^2$ at 11.0 V, a luminous efficiency of 12.5 cd/A at $20\;mA/cm^2$, a power efficiency of 6.50 lm/W at $20\;mA/cm^2$, and $CIE_{x,y}$ coordinates of (x = 0.173, y = 0.306) at 8.0 V, all of which demonstrate the superiority of these materials in blue OLEDs.

• KIEAE Journal
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• v.8 no.6
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• pp.21-26
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• 2008

According to the tendency of energy efficiency and environment-friendly chracteristics, demend of High-efficiency lighting using LED(Light Emitting Diode)are being increased actively and applied in various fields. However, In order to adequate application of LED light sources, it is necessary to lighting environment and luminous characteristics of LED light sources. This Study aims to characterize the work-plane lighting environment by LED light sources comparing with fluorescent light sources which are widely used. For the sake of this study, a fluorescent light source and 5 LED light sources were introduced and luminance and correlated color temperature were measured to evaluate luminance contrast. The experimental model is Mock-up which is $4.9m{\times}7.2m$ with a height of 2.9m. The test room was set up partition and desks. Luminance and correlated color temperature were measured work-plane on the desk which was set up local lighting by the Radiant Imaging ProMetric 1400. The optical characteristics data of LED can give a lot of advantages to design LED lighting appliances. Hereafter, the object of research will be conducted to evaluate effects of LED light sources on working performance, survey of visual performance, preference and physiology of subjects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04a
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• pp.65-69
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• 2009

Generally Lighting system consists of lamp and luminaire. When a fluorescent lamp is installed in luminaire, power and light output is changed by ambient temperature. Particularly electrodeless lamp depends on the changes that are mercury pressure with amalgam temperature and magnetic properties with ferrite temperature. It has finally influence on optical efficiency. In this study, the temperature change of ferrite and cold spot, vessel are measured at transitional state and then same characteristics are measured with increase of ambient temperature. At transitional state, luminous flux is related to temperature change of cold spot that compare with behavior of mercury pressure and light output. At increase of ambient temperature, we analyzed change that efficiency and electrical, optical characteristics of electrodeless lamp are related to ferrite core and cold spot temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1429-1432
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• 2007

We fabricated white organic light emitting diodes(WOLED) having two complementary and three primary colors with emission layers of DPVBi / MADN : DCM2-0.5% and DPVBi / $Alq_3$ / MADN : DCM2-1.5%, respectively. WOLED using three primary colors shows broad electroluminescence including green emission peak at 510nm while optical properties of the two complementary WOLED was higher current efficiency of 6.2 cd/A than 4.9 cd/A of three primary color WOLED. The maximum luminescence of WOLED with two complimentary color was $15200cd/m^2$ along with luminous efficiency 6.2cd/A, as achieving stable white color coordinates for both of WOLEDs at (0.33 , 0.33) almost.

• 한국정보디스플레이학회:학술대회논문집
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• 2001.08a
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• pp.209-212
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• 2001

We report the synthesis and characterization of new alkoxy substituted spirobifluorene derivatives. The spiro compounds having alkoxy hydrocarbon chains were readily soluble in common organic solvents, having improved film-forming properties and had a significantly reduced tendency to crystallize, resulting in increasing their service lifetime. The results of DSC showed that it was amorphous. The optical and electroluminescent spectra were characterized. Electroluminescence (EL) properties of three-layer light emitting diodes (LED) of $ITO/TPD/spirobifluorene/Alq_3/LiF/Al$ as the active layer were characterized. Blue emission peaking of the EL spectrum of the three-layer device at 402 nm and a luminance of 3,125 $cd/m^2$ were achieved at a drive voltage 12.8 V. The luminous efficiency was obtained to be 1.7 lm/W. The color coordinate in CIE chromaticity is (0.16, 0.09), which is in a pure blue region. The external quantum efficiency was obtained to be 2.0%. The results indicate that the spirobifluorene compounds having alkoxy hydrocarbon chains are strongly potential blue emitters for LED applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.956-960
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• 2006

Deep-blue organic light-emitting diodes (OLEDs) with/without ultra-thin LiF layer inserted at the interface between hole-blocking and electron-transporting layers have been fabricated and investigated. The fundamental structures of the OLEDs are ITO/m-MTDATA/NPB/BCP/LiF (with/ without)/ $Alq_3/LiF/Al.Deep$ blue light emission with CIE coordinate of (0.15, 0.11) has been achieved for all devices. Further, by inserting LiF with thickness of 1nm at the interface between BCP and $Alq_3$ layer, the luminous efficiency as well as the power efficiency is much improved compared to that without. The enhancement of electron injection due to insertion of LiF may account for this improvement.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.940-943
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• 2003

We report the fabrication and the characterization of white organic light-emitting devices consisting of a red-emitting layer of a new DCM derivative doped into 4,4'bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (${\alpha}-NPD$) and a blue-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi). The device structure is ITO/PEDOT:PSS/${\alpha}-NPD$ (50 nm)/${\alpha}-NPD$:DCM (5 nm, 0.2 %)/DPVBi (x)/Alq3 (40 nm)/LiF (0.5 nm)/Al. The electroluminescence (EL) spectra consist of two broad peaks around 470 nm and 580 nm with the spectral emission depending on the thickness of DPVBi. The device with the DPVBi thickness of about 20 nm show a white light-emission with the Commission Internationale d'Eclairage(CIE) chromaticity coordinates of (0.33, 0.36). The external quantum efficiency is 2.6% and luminous efficiency is 2.0 lm/W at a luminance of 100 $cd/m^{2}$. The maximum luminance is about 30,270 $cd/m^{2}$ at 13.9 V.