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In a thick-dielectric electroluminescent (TDEL) device, which is a variation of thin-film electroluminescent devices, one of the insulation layers is replaced by a thick-film dielectric layer. High brightness and reliability are the features of TDEL owing to a higher withstanding voltage of the thick-film dielectric layer. This paper presents a new type of TDEL with a bottom emission structure. The thick-film dielectric layer was manufactured by spin coating using an ink material, which is a mixture of BaTiO3 powder and a binder resin. The thicknesses of the phosphor and dielectric layers were minimized to reduce the operating voltage. A threshold voltage as low as 50 V and a maximum luminance of 1000 cd/m2 were obtained at 60 V. [ABSTRACT FROM AUTHOR]

In this study, TiO2-ZnO:Yb3+/Ho3+ upconversion phosphors are synthesized by a solid-phase reaction method and their Yb3+ concentration dependence is analyzed. The crystal structure of the phosphors is analyzed by X-ray diffractometry, where each sample is composed of Zn2TiO4 and Yb2Ti2O7. Photoluminescence characteristics are analyzed and peaks are observed at wavelengths of 539 nm (5F4, 5S2 → 5I8) and 669 nm (5F5 → 5I8). High intensity luminescence is obtained for samples with Yb = 7–8 mol%. Analysis of temperature characteristics shows absolute and relative sensitivities of 0.0052 K−1 and 0.40% K−1, respectively. The samples are found to be chemically stable, indicating that TiO2-ZnO:Yb3+/Ho3+ could be used as a temperature sensor. [ABSTRACT FROM AUTHOR]

A ZnS:Mn phosphor film for an inorganic electroluminescent (EL) device fabricated by metal precursor sulfurization was evaluated. Metallic ZnMn was thermally evaporated at room temperature and then sulfurized by sulfur gas flowing in a tube furnace at various temperatures from 400 to 800 °C. X-ray diffraction, energy dispersive x-ray spectroscopy, and photoluminescence observations indicated that a ZnS:Mn phosphor layer was formed after sulfurization. A thick-dielectric EL device was manufactured using the obtained ZnS:Mn phosphor. The EL luminance of 216 cd/m2 at 1.0 kHz was measured when the phosphor layer was sulfurized at 500 °C. A charge density versus voltage (Q-V) curve was also analyzed to evaluate the EL phosphor characteristics. [ABSTRACT FROM AUTHOR]

This study synthesized LaF3–LaOF:Yb3+/Ho3+via a solid-state reaction method and analyzed its optical properties and temperature sensitivity. Specifically, the crystalline structure of each sample—composed of LaOF (tetragonal) and LaF3 (hexagonal)—were analyzed under X-ray diffraction. In addition, their photoluminescence (PL) properties were analyzed, with peaks observed at 543, 654, and 755 nm. The highest PL intensity was observed at 543 nm for a molar ratio of La:Yb:Ho = 1:0.05:0.001. Furthermore, the temperature characteristics of each sample were analyzed to determine the absolute and relative sensitivities as 0.0232 K−1 and 0.357 %K−1, respectively. [ABSTRACT FROM AUTHOR]

The local ordering of particles is considered an important process in glass transition. Ordering is usually observed in simulation and micrometer-sized colloid. However, clear information on local ordering at the molecular level is difficult to obtain experimentally. In this study, we prepared an easily glass-forming fluorophore with a color change owing to the intermolecular arrangement in the liquid, glass, and crystal states. The bathochromic shifts of the photoluminescence spectra indicated a change in the intermolecular orientation upon immediate cooling of the melt. The recovery of the spectra by successive heating indicated that rotation contributed to the change in the intermolecular orientation. The orientation in the glass was distinct from that during crystal growth, which was observed as a slow bathochromic shift by maintaining the temperature between the melting points of the blue- and green-luminescent crystals obtained from dichloromethane/ethanol and dichloromethane/hexane, respectively. Our results demonstrate that the anisotropic interaction between glass-forming luminophores is useful for uncovering molecular-level events in the glassy state. [ABSTRACT FROM AUTHOR]