• Journal of the Korean Applied Science and Technology
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• v.18 no.3
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• pp.186-190
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• 2001

By fabricating the organic light-emitting devices (OLEDs) based on phosphorescent material, the internal quantum efficiency can reach 100%, compared to 25% in the case of the fluorescent material. Thus, the phosphorescent OLEDs have recently been extensively studied and showed higher internal quantum efficiencies then the conventional OLEDs. In this study, we investigated the characteristics of the phosphorescent OLEDs, with the green emitting phosphor, $Ir(ppy)_{3}$, (tris(2-phenylpyridine)iridium). The devices with a structure of $ITO/TPD/Ir(ppy)_{3}$ doped in the host material $/BCP/Alq_{3}/Li:Al/Al$ were fabricated, and its electrical and optical characteristics were studied. By changing the doping concentration of $Ir(ppy)_{3}$, we fabricated several devices and investigated the device characteristics. OLEDs doped into BCP by 10% showed the best characteristics. For 10% doped OLEDs, the maximum luminance of was over 10000 $cd/m^{2}$, and the maximum power efficiency was 7.14 lm/W.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.510-511
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• 2005

Several iridium based complexes were investigated as blue phosphorescent dopants. They are achieved about 100 % quantum efficiencies due to utilization of both singlet and triplet excitons in the radiative processes. We have fabricated phosphorescent OLED with 8 % Ir$(ppz)_3$ as a triplet emissive dopnat in diverse host materials. In this study, the CBP obtained the luminance efficiency of 0.20 cd/A adapts to the host material. Furthermore, we synthesize metalorganic phosphor complexs based on Ir heavy metal with different ligands as to $Ir(ppz)_2acac$, $(Im)_2Ir(acac)$, $(Im-R)_2Ir(acac)$.

• Korean Journal of Materials Research
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• v.8 no.8
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• pp.737-743
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• 1998

The synthesis of $SrAI_2O_4:Eu^{2+}$ phosphor and its properties of both photoluminescence and long-phosphorescent were investigated as a function of sintering condition. Single phase of $SrAl_2O_4$ was obtained by sintering the mixtures of $SrCO_3$, $Eu_2O_3$, $AI_2O_34 and 3wt% $B_2O_3$ powders over 100$0^{\circ}C$ in Ar/H2 atmosphere. The optimum sintering condition for the long-phosphorescent phosphor of $SrAI_2O_4:Eu^{2+}$ was found at 130$0^{\circ}C$ for 3hours. The PL emission spectrum of $SrAI_2O_4:Eu^{2+}$ shows a maximum peak intensity at 520nm(2.384eV) with a broad emission extending from 450 to 650nm which resulted from the $4f^65d^1$$\rightarrow$$4f^7$ transition of $Eu^{+2}$ under 360nm exitation. Monitored at 520nm. the excita¬tion spectrum of $SrAI_2O_4:Eu^{2+}$ exhibits a maximum peak intensity at 360nm (3.44eV) with a broad absorption band extending from 250 to 480nm.

• Korean Journal of Materials Research
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• v.26 no.10
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• pp.561-569
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• 2016

$SrAl_2O_4$: $Eu^{2+}$ and $Dy^{3+}$ phosphorescent phosphors were synthesized using the polymerized complex method. Generally, phosphorescent phosphors synthesized by conventional solid state reaction show a micro-sized particle diameter; thus, this process is restricted to applications such as phosphorescent ink and paint. However, it is possible to synthesize homogeneous multi-component powders with fine particle diameter by wet process such as the polymerized complex method. The characteristics of $SrAl_2O_4$: $Eu^{2+}$ and $Dy^{3+}$ powders prepared by polymerized complex method with one and two step calcination processes were comparatively analyzed. Temperatures of organic material removal and crystallization were observed through TG-DTA analysis. The crystalline phase and crystallite size of the $SrAl_2O_4$: $Eu^{2+}$ and $Dy^{3+}$ phosphorescent phosphors were analyzed by XRD. Microstructures and afterglow characteristics of the $SrAl_2O_4$: $Eu^{2+}$ and $Dy^{3+}$ phosphors were measured by SEM and spectrofluorometry, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.715-718
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• 2004

Substantially improved methods for the preparation of europium-doped yttrium oxide red phosphor with the inclusion of alkali metal halides having a general formula $(Y_{1-x}Eu_x)_2O_3$:MX where 0.025${\leq}$x${\leq}$0.2 and MX is alkali halide in the mole ratio 0.025 to 0.6, more preferably between 0.05 to 0.2 mole, are reported. Another series of the red phosphor materials with general formula $(Y_{1-x-y}Gd_xEu_y)_2O_3$:MX where 0.05${\leq}$x${\leq}$0.40 and 0.025${\leq}$y${\leq}$0.20 and MX is alkali halide in the mole ratio 0.025 to 0.5, more preferably between 0.1 to 0.2 mole, has also been presented. The inclusion of alkali halide greatly increase the luminance of the materials. The materials are very soft with fine particle size less than 100nm. The phosphorescent materials have good luminance in VUV region.

• Journal of the Korean Ceramic Society
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• v.50 no.1
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• pp.50-56
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• 2013

Phosphorescent materials coated with titanium dioxide were fabricated and photocatalytic reactions between these materials and VOCs gases were examined. A thin film (approx. 100 nm) of nanosized $TiO_2$ was deposited on the $Sr_4Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^+$ phosphor using low-pressure chemical vapor deposition (LPCVD). The characteristics of the photocatalytic reaction were examined in terms of the decomposition of benzene gas using a gas chromatography (GC) system under ultraviolet (${\lambda}$ = 365 nm) and visible light (${\lambda}$ > 420 nm) irradiation. $TiO_2$-coated $Sr_4Al_{14}O_{25}$ : $Eu^{2+}$, $Dy^{3+}$, $Ag^+$ phosphor showed different photocatalytic behavior compared with pure $TiO_2$. $TiO_2$-coated phosphorescent materials showed a much faster photocatalytic decomposition of benzene gas under visible irradiation compared to the pure $TiO_2$ for which the result was practically negligible. This suggests that the extension of the absorption wavelength to visible light occurred through energy band bending by a heterojunction at the interface of the $Sr_4Al_{14}O_{25}-TiO_2$ composite. Also, the $Sr_4Al_{14}O_{25}-TiO_2$ composite showed the photocatalytic decomposition of benzene in darkness due to the photon light emitted from the $Sr_4Al_{14}O_{25}$ phosphors.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.333-337
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• 2006

In this study, the $Sr_{1-x}Ba_{x}Al_{2}O_{4}:Eu^{2+},Dy^{3+}$ phosphor were prepared by the solid-state reaction method and its photoluminescence properties were investigated. Starting powders of $SrCO_3,\;BaCO_3,\;and\;Al_{2}O_3$ were mixed with $Eu_{2}O_3$ as activator, $Dy_{2}O_3$ as co-activator and $B_{2}O_3$ as flux. Then, the mixed powders were heated at the temperature of $1100{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of $95%Ar+5%H_2$. The effect of Ba addition from 0.0 to 1.0 mol on photoluminescence was investigated. As the amount of Ba increased, the intensity of emission increased and the optimum long phosphorescence occurred at the amount of 0.1 mol Ba. The optimum sintering condition for long phosphorescent phosphor of $Sr_{1-x}Ba_{x}Al_{2}O_{4}:Eu^{2+},Dy^{3+}$($x=0{\sim}1.0mol$) was found at $1400^{\circ}C$. The excitation spectra showed a broad band of $250{\sim}450nm$ with maximum peak at 360 nm. The maximum peak intensity of emission spectra occurred at the range of $480{\sim}520nm$, depending on Ba content.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.193-200
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• 2016

Characteristics of $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphorescent phosphors synthesized by solid state reaction and polymerized complex method were comparatively analyzed. In order to evaluate thermal stability of $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphorescent phosphors at high temperature, phosphorescent properties of $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ were investigated with thermal treatment at $1250^{\circ}C$ under reducing atmosphere, which was the general heat treatment conditions for ceramic manufacturing process. The phosphorescent properties of thermally treated $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphors synthesized by solid state reaction and polymerized complex method were investigated. The crystal structure and crystallite size were observed through XRD analysis. Microstructure and particle size of thermally treated $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphors were analyzed by SEM and PSA. Photoluminescence and afterglow characteristics of thermally treated $SrAl_2O_4:Eu^{2+}$, $Dy^{3+}$ phosphorescent phosphors were measured by spectrofluorometer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.315-319
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• 1999

Properties of both photoluminescence and long-phosphorescent for Eu, Dy-codoped $SrAl_2O_4$ powder phosphor synthesized by solid reaction method were investigated by PL instrument. Two intense peaks in the emission spectrum measured at 10 K are observed near 450 nm (2.755 eV) and 520 nm (2.384 eV) wavelength, but at 300 K the main peak of 520 nm wavelength is presented. After the removal of light excitation (360 nm), the excellent after-glow characteristic of the phosphorescence were obtained as a result of low decay tiem, although the after-glow intensities of phosphor vary exponentially with the times.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.473-477
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• 2015

In this paper, a commercial phosphorescent white light-emitting diode (WLED) visible light communication (VLC) system with an equalization circuit to achieve the high modulation bandwidth was designed and demonstrated. An analytical method to examine the performance of the equalizer was carried out using a general circuit-simulator, PSpice. The equalization circuit was composed of two passive filters with resisters and a capacitor and an active filter with an op-amp. Utilizing our post-equalization technology, the ~3.5 MHz bandwidth of phosphor WLED could be extended to ~25 MHz without using an optical blue-filter. In this VLC system with a single round-type WLED and a single PIN photo-diode, ASK data transmission up to 35 Mbps at a 1m free space distance was obtained. The resulting bit-error-rate was $7.6{\times}10^{-4}$, which is less than the forward error correction (FEC) limit of $3.8{\times}10^{-3}$.