• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.387-392
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• 2019

$Dy^{3+}$ and $Eu^{3+}$-co-doped $La_2MoO_6$ phosphor thin films were deposited on sapphire substrates by radio-frequency magnetron sputtering at various growth temperatures. The phosphor thin films were characterized using X-ray diffraction (XRD), scanning electron microscopy, ultraviolet-visible spectroscopy, and fluorescence spectrometry. The optical transmittance, absorbance, bandgap, and photoluminescence intensity of the $La_2MoO_6$ phosphor thin films were found to depend on the growth temperature. The XRD patterns demonstrated that all the phosphor thin films, irrespective of growth temperatures, had a tetragonal structure. The phosphor thin film deposited at a growth temperature of $100^{\circ}C$ indicated an average transmittance of 85.3% in the 400~1,100 nm wavelength range and a bandgap energy of 4.31 eV. As the growth temperature increased, the bandgap energy gradually decreased. The emission spectra under ultraviolet excitation at 268 nm exhibited an intense red emission line at 616 nm and a weak emission line at 699 nm due to the $^5D_0{\rightarrow}^7F_2$ and $^5D_0{\rightarrow}^7F_4$ transitions of the $Eu^{3+}$ ions, respectively, and also featured a yellow emission band at 573 nm, resulting from the $^4F_{9/2}{\rightarrow}^6H_{13/2}$ transition of the $Dy^{3+}$ ions. The results suggest that $La_2MoO_6$ phosphor thin films can be used as light-emitting layers for inorganic thin film electroluminescent devices.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2849-2853
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• 2010

A method to improve the photocatalytic activity of titanium dioxide by modification with a sensitizer and a metal oxide is proposed. To achieve this goal, we used metal oxides as dopants. In particular, $CaWO_4$ and $Gd_2O_2S$:Tb were used because their 2.6 eV and 2.2 eV band gap energy and optical properties have a large positive effect on photocatalysis. The improvement in the photocatalytic activity of $TiO_2$ modified with $Gd_2O_2S$:Tb under ultraviolet light irradiation is described in a previous study. The present work focuses on the sensitization of metal oxide-modified $TiO_2$. Having observed the ultraviolet-visible absorption spectra of 3,4,9,10-Perylenetetracarboxylic diimide in the wide visible-light region from 400 nm to 650 nm and the broad peaks in its photoluminescence spectra at 695 nm and 717 nm, we decided to use this perylene dye to sensitize modified $TiO_2$ to enhance its activity as a visible-light harvesting photocatalyst. We also explored the positive effects thin-film surface changes stemming from ultraviolet pre-treatment have on photocatalytic activity. Finally, we subjected several metal oxide-modified $TiO_2$ products sensitized by the perylene dye to ultraviolet pre-treatment, obtaining the most active photocatalysts.

• Current Optics and Photonics
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• 제5권1호
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• pp.1-7
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• 2021

For higher sensitivity in ultraviolet (UV) and even vacuum ultraviolet (VUV) detection of silicon-based sensors, a sandwich-structured film sensor based on Ag Localized Surface Plasmon Resonance (LSPR) was designed and fabricated. This film sensor was composed of a Ag nanoparticles (NPs) layer, SiO2 buffer and fluorescence layer by physical vapour deposition and thermal annealing. By tuning the annealing temperature and adding the SiO2 layer, the resonance absorption wavelength of Ag NPs matched with the emission wavelength of the fluorescence layer. Due to the strong plasmon resonance coupling and electromagnetic field formed on the surface of Ag NPs, the radiative recombination rate of the luminescent materials and the number of fluorescent molecules in the excited state increased. Therefore, the fluorescent emission intensity of the sandwich-structured film sensor was 1.10-1.58 times at 120-200 nm and 2.17-2.93 times at 240-360 nm that of the single-layer film sensor. A feasible method is provided for improving the detection performance of UV and VUV detectors.

• Current Photovoltaic Research
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• 제4권1호
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• pp.8-11
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• 2016

Strong deep ultraviolet emitting aniline and $TiO_2$ composite has been synthesized via hydrolysis and condensation reactions of titaniumisopropoxide ($Ti(OPr)_4$), aniline, and acetic anhydride. Three different weight ratios of aniline and $Ti(OPr)_4$ including 3:1 ($TiO_2An-A$), 2:1 ($TiO_2An-B$), and 1:1 ($TiO_2An-C$) were synthesized and characterized their optical properties. The FTIR spectra of the $TiO_2An-A$, -B, and -C showed the absorption intensities of the benzene ring stretching and bending vibrations, and benzene ring -CH stretching, bending, and deformation vibrations increased with the increase of the amount of aniline. The UV-visible absorption spectra showed that the UV region absorption was slightly increased with the increase of the amount of aniline. The photoluminescence (PL) intensities were exponentially increased with the increase the excitation wavelength from 307 to 317 nm, steadily increased from 300 to 313 nm and slowly increased from 302 to 308 nm for $TiO_2An-A$, -B, and -C, respectively and decreased thereafter. Therefore, the PL intensity is strongly dependent on the weight ratio of $Ti(OPr)_4$ and aniline.

• The Korean Journal of Ceramics
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• 제3권4호
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• pp.245-248
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• 1997

Photoluminescence (PL) and cathodoluminescence (CL) characteristics of Ce-activated $Y_{2-x}Ce_xSiO_5$ have been investigated as functions of Ce concentration and firing condition. According to the X-ray, PL and CL results, $Y_2SiO_5$ is found to have two phases depending on the firing temperature. For the specimen fired above 127$0^{\circ}C$, the emission band peaked at 395nm with a shoulder at 424 nm under ultraviolet (u.v.) and cathode-ray (c.r.) excitation. However, for the specimen fired below 120$0^{\circ}C$ in air the peak was observed at 424 nm and it shifted to longer wavelength with reduction level. The reduced specimen for x=0.02 showed the brightest emission under u.v. excitation whereas under c.r. excitation the brightest emission was observed for the reduced specimen for x=0.06.

• Applied Science and Convergence Technology
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• 제27권3호
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• pp.52-55
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• 2018

We reported a new method to enhance the photoluminescence (PL) properties of $Eu^{3+}$ ions doped $Gd_2Mo_4O_{15}$ phosphors via cation substitution. With the aid of conventional sol-gel method, a series of $Eu^{3+}$ ions doped $Gd_{2(1-x)}Y_{2x}Mo_4O_{15}$ phosphors were prepared. The prepared samples emitted red light when excited at 393 nm. Moreover, when part of the $Gd^{3+}$ ions was substituted by the $Y^{3+}$ ions, the PL emission intensity of the studied samples was enhanced and the optimal doping concentration for $Y^{3+}$ ions was 30 mol%. The calculated CIE coordinate (0.663,0.337) was situated in the red region. Furthermore, the thermal quenching behaviors of the synthesized $Eu^{3+}$ ions doped $Gd_{2(1-x)}Y_{2x}Mo_4O_{15}$ phosphors were studied. At last, we also packaged a red-emitting light-emitting diode device by integrating the obtained phosphors and a near-ultraviolet chip to verify the applications of the $Eu^{3+}$ ions doped $Gd_{2(1-x)}Y_{2x}Mo_4O_{15}$ phosphors for indoor lighting.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.811-814
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• 2002

$(Ba,Sr)_2SiO_4:Eu^{2+}$ phosphor particles with high brightness were prepared by spray pyrolysis. The changes in the photoluminescence intensity and morphology of $(Ba,Sr)_2SiO_4:Eu^{2+}$ were investigated by changing the posttreatment temperature and the concentration of dopant. The prepared $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles has a dense structure, but irregular shape after the posttreatment. When they were excited by the ultraviolet light of 410 nm, a broad emission band with a peak at 508 nm was observed. The photoluminescence intensity of the prepared $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles was enhanced by increasing the posttreatment temperature up to 1300 $^{\circ}C$ and further improved by adding several rear-earth codopants. The $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles prepared by spray pyrolysis had a good excitation spectrum in the wavelength longer than 350 nm. Therefore, it was concluded that the $(Ba,Sr)_2SiO_4:Eu^{2+}$ prepared by spray pyrolysis is a good green-emitting phosphor for LED application.

• 한국재료학회지
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• 제18권3호
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• pp.137-142
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• 2008

Blue-emitting BAM:Eu phosphor powders were formed by post-treatment of precursor powders with hollow or dense morphologies. The morphologies of the precursor powders obtained by spray pyrolysis were controlled by changing the preparation conditions and by changing the type of spray solution. The effects of the morphologies of the precursor powders on the characteristics of the BAM : Eu phosphor powders reacted with $AlF_3$ flux were investigated. Precursor powders with a spherical shape and a hollow morphology produced BAM : Eu phosphor powders with a plate-like morphology, a fine size and a narrow size distribution. On the other hand, precursor powders with a spherical shape and dense morphology produced BAM : Eu phosphor powders with a plate-like morphology and a large size. $AlF_3$ flux improved the photoluminescence intensities of the BAM : Eu phosphor powders. The photoluminescence intensity of the fine-sized BAM : Eu phosphor powders with a plate-like morphology was 90% of the commercial product under vacuum ultraviolet conditions.

• Journal of Information Display
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• 제12권2호
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• pp.93-96
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• 2011

Single-phased $CaZrO_3:Dy^{3+}$, $Tm^{3+}$ series have been successfully synthesized by solid-state reaction, and their luminescence properties were investigated. Under 355 nm excitation, $CaZrO_3:Dy^{3+}$ series showed characteristic emission of $Dy^{3+}$, which exhibited yellowish white color. By introducing $Tm^{3+}$ into the matrix, the emitted hue of the $Dy^{3+}$-doped sample could be easily tailored to white, and simultaneously, energy transfer from $Tm^{3+}$ to $Dy^{3+}$ was observed. The color coordinates of the optimum white-emitting sample were (0.321, 0.323), which were very close to the data of the National Television Standard Committee (0.33, 0.33). The co-activated phosphors presented good match to ultraviolet light-emitting diodes (LEDs), which revealed that they could be novel promising phosphors utilized in white LED application.

• Transactions on Electrical and Electronic Materials
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• 제15권5호
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• pp.249-252
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• 2014

The aim of this work is to investigate the effect of $Ca_xSr_{2-x}$ and activator on the structural and luminescent properties of green-emitting $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ nano phosphor. Using urea as fuel and ammonium nitrate as oxidizer, $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ has been successfully synthesized, using a combustion method. The particles were found to be small, spherical and of round surface. SEM imagery showed that the phosphors particles are of nanosize. The $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ emission spectrum for 360 nm excitation showed a single band, with a peak at 490 nm, which is a green emission. The highest luminous intensity was at $1,000^{\circ}C$, which was obtained when the $Eu^{2+}$ content (y) was 0.05. The results support the application of $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor as a fluorescent material for ultraviolet light-emitting diodes (UV-LEDs). Characteristics of the synthesized $Ca_xSr_{2-x}SiO_4:Eu^{2+}$ phosphor were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and photoluminescence (PL) detection.