• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.121-124
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• 1998

Generally the structure of powder electroluminescent devices (PELDs) on ITO-film was makeup of the ZnS:Cu phosphor layer and BaTiO$_3$ insulating layer. The active layer, which consists of a suitably doped ZnS powder mixed in a dielectric, is sandwiched between two electrodes; one of which are ITO film and the other is aluminum. In this paper, three kinds of powder eleotroluminescent devices (PELDs) : WK-A(ITO/BaTiO$_3$/ZnS:Cu/Silver paste). WK-B(ITO/BaTiO$_3$+ZnS:Cu/Silver paste) and WK-C(ITO/BaTiO$_3$/ZnS:Cu/BaTiO$_3$/Silver paste), fabricated by spin coating method, were investigated. To evaluate the luminescence properties of three kinds of PELDs, EL emission spectroscopy, transferred charge density and time response of EL emission intensity under square wave voltage driving were measured.

• Journal of the Semiconductor & Display Technology
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• v.20 no.2
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• pp.73-76
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• 2021

This thesis described the optical and electrical properties of the alternating current powder electroluminescent device based on Ag nanowire as a transparent electrode. The Ag nanowire electrode showed the morphology of 20 nm in diameter and 15 ㎛ in length. The transparent electroluminescent devices that were fabricated using the nanomilled ZnS : Cu, Mn phosphor by bar-coating process showed the transmittance of 67%. In order to improve the luminous efficiency, it is necessary to apply the transparent dielectric layer and increase the amount of the nanophosphor while maintaining the transmittance.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.447-453
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• 2011

The monodisperse spherical $SiO_2$ particles were overcoated with $Y_2O_3:Eu^{3+}$ phosphor layers via a Pechini sol-gel process and the resulting $SiO_2@Y_2O_3:Eu^{3+}$ core-shell phosphors were subsequently annealed at $800^{\circ}C$ at an ambient atmosphere. The crystallographic structure, morphology, and luminescent property of core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The spherical, nonagglomerated $SiO_2$ particles prepared by a Stober method exhibited a relatively narrow size distribution in the range of 260-300 nm. The thickness of phosphor shell layer in the core-shell particles can be facilely controlled by varying the coating number of $Y_2O_3:Eu^{3+}$ phosphors. The core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors showed a strong red emission, which was dominated by the $^5D_0-^7F_2$ transition (610 nm) of $Eu^{3+}$ ion under the ultraviolet excitation (263 nm). The PL emission properties of $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were also compared with pure $Y_2O_3:Eu^{3+}$ nanophosphors.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.7
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• pp.521-524
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• 1999

Nb silicide was formed on the Si micro-tip arrays in order to improve field emission properties of Si-tip field emitter array. After silicidization of the tips, the etch-back process, by which gate insulator, gate electrode and photoresist were deposited sequentially and gate holes were defined by removing gradually the photoresist by $O_2$ plasma from the surface, was applied. Si nitride film was used as a protective layer in order to prevent oxygen from diffusion into Nb silicide layer and it was identified that the NbSi2 was formed through annealing in $N_2$ ambient at $1100^{\circ}C$ for 1 hour. By the Nb silicide coating on Si tips, the turn-on voltage was decreased from 52.1 V to 32.3 V and average current fluctuation for 1 hour was also reduced from 5% to 2%. Also, the fabricated Nb silicide-coated Si tip FEA emitted electrons toward the phosphor and light emission was obtained at the gate voltage of 40~50 V.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.1
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• pp.1-8
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• 2015

To produce the white light, there are a single chip method using the blue light and phosphor coating, a multi chip method by mixing R, G, B light.. Multi chip method is proper for the smart lighting system by controling color and color temperature. And color rendering of single chip LED is good by even spectral distribution. To apply application technic like smart light system, this paper analyzed the properties of single chip LED and RGB multi chip LED, and implemented the 2 part subject evaluation for single chip LED and RGB multi chip LED. The first part is comparison of properties for single chip LED and RGB multi chip and second part is color appearance evaluation of 8 colors in each lighting environment.

• Applied Microscopy
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• v.47 no.1
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• pp.55-62
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• 2017

This paper describes experiments aimed at characterizing the behavior of field electron emitters fabricated by coating carbon fibers with epoxylite resin. Polyacrylonitrile carbon fibers of type VPR-19, thermally treated at $2,800^{\circ}C$, were used. Each was initially prepared in a "uncoated" state, by standard electro polishing and cleaning techniques, and was then examined in a scanning electron microscope. The fiber was then baked overnight in a field electron microscope (FEM) vacuum chamber. Current-voltage characteristics and FEM images were recorded on the following day or later. The fiber was then removed from the FEM, coated with resin, "cured" by baking, and replaced in the FEM. After another overnight bake, the FEM characterization measurements were repeated. The coated fibers had significantly better performance than uncoated fibers. This confirms the results of earlier experiments, and is thought to be due in part to the formation of a conducting channel in the resin over layer. For the coated fiber, lower voltages were needed to obtain the same emission current. The coated fibers have current-voltage characteristics that show smoother trends, with greater stability and repeatability. No switch-on phenomena were observed. In addition, the emission images on the phosphor-coated FEM screen were more concentrated, and hence brighter.

• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.32-36
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• 2007

Zinc gallate $(ZnGa_2O_4)$ thin film phosphors have been formed on ITO glass substrates by a sol-gel spinning coating method. For the formation of the film phosphors, the starting materials of zinc acetate dihydrate, gallium nitrate hydrate and 2-methoxyethanol as a solution were used. The thin films deposited were firstly dried at $100^{\circ}C$ and fired at $500^{\circ}C\;or\;600^{\circ}C$ for 30 min and then, annealed $500^{\circ}C\;or\;600^{\circ}C$ at for 30 min under an annealing atmosphere of 3% $H_2/Ar$. The thin films deposited on ITO glass plates showed the (220), (222), (400), (422), (511), and (440) peaks of spinel structure as well as the (311) peak indicating a standard powder diffraction pattern. The surface morphologies of the thin film phosphors were observed with a firing and an annealing condition. The $ZnGa_2O_4$ film phosphors showed the blue emission spectra around 410 nm as well as the emission spectra in the UV region (360-380 nm).

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1379-1381
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• 1998

Powder electroluminescent device (PELD) structured conventionally dielectric and phosphor layer, between electrode and their layer fabricated by screen printing splaying or spin coating method. To promote performance of PELDs, we approached the experiments for different structure and thickness variation of PELD. Thickness variation($30{\mu}m{\sim}130{\mu}m$) was taken. To investigate electrical and optical properties of PELDs, EL spectrum, transferred charge density using Sawyer-Tower's circuit brightness was measured. Variation of structure in PELDs was as follows: WK-1 (ITO/BaTiO3/ZnS:Cu/Silver paste), WK-2 (ITO/BaTiO3/ZnS:Cu/BaTiO3/ZnS:Silver paste), WK-3 (ITO/BaTiO3/ZnS:Cu/BaTiO3/Silver paste), WK-4(ITO/BaTiO3+ZnS:Cu/Silver paste) As a result, structure of the highest brightness appeared WK-4 possessed 60 ${\mu}m$ thickness. The brightness was 2719 cd/$m^2$ at 100V, 400Hz.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.209-211
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• 2008

본 연구에서는 실리케이트 적색 형광체의 신뢰성을 향상시키기 위하여 $SiO_2$ 박막을 졸-겔(sol-gel) 방법으로 코팅하였으며, 봉지재의 종류에 따른 코팅된 형광체의 신뢰성 변화를 조사하였다. 졸-겔 코팅 후 형광체 표면을 관찰한 결과 졸-겔 코팅이 잘 이루어 졌음을 알 수 있었으며, 4회 코팅 후 박막의 두께는 약 150nm였다. 코팅하지 않은 형광체의 경우 봉지재에 따른 차이는 있었지만 500시간 경과 후 효율 감소율은 30% 이상이었으며 코팅 한 형광체의 경우는 에폭시, JCR6175가 10${\sim}$25%, EG6301은 10% 이내의 효율 감소율을 보였다. 한편 색좌표 경우 에폭시 봉지재가 약 0.02의 변화를 EG6301 봉지재의 경우 0.01 이내의 변화를 보였다.

• Bulletin of the Korean Chemical Society
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• v.28 no.8
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• pp.1280-1284
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• 2007

A series of Ca1-xSrxS:Eu (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) phosphors were synthesized by solid-state reactions. The Ca1-xSrxS:Eu phosphors have a strong absorption at 455 nm, which corresponds to the emission wavelength of a blue LED. The emission peak of Ca1-xSrxS:Eu is blue shifted from 655 to 618 nm with increasing Sr content. The characteristics of Ca1-xSrxS:Eu phosphors make them suitable for use as wavelengthtunable red-emitting phosphors for three-band white LEDs pumped by a blue LED. In support of this, we fabricated a three-band white LED by coating SrGa2S4:Eu and Ca0.6Sr0.4S:Eu phosphors onto a blue LED chip, and characterized its optical properties.