Shinnosuke Kamei

Synthesis of arylsulfanyl-subphthalocyanines and their ring expansion reaction

For dye-sensitized solar cells, phthalocyanines require strong absorption of far-red light between 700 and 850 nm because of their high electron transfer efficiency. Nevertheless phthalocyanines lack of affinity to basal plats, they inhibit utilization as dye-sensitized solar cell photosensitizer. Then, subphthalocyanines are used as precursors to prepare asymmetric 3:1 type phthalocyanines using a ring-enlargement technique to give affinity to basal plates. As subphthalocyanines having arylsulfanyl substituents used as a precursor, asymmetric phthalocyanines are expected to have good affinity to basal plates. Spectroscopic properties and electron transfer abilities to synthesize non-peripheral arylsulfanyl-subphthalocyanines were estimated. In addition to prepare as trial, asymmetric 3:1 type phthalocyanine, hexakis[(4-methylphenyl)thio]phthalocyanine, was synthesized from corresponding subphthalocyanine.

Fluorescence Properties and Synthesis of Green-Emitting Tb3

The excitation wavelength of conventional Tb3+-activated phosphor is near 270 nm. This study describes novel green-emitting Tb3+-activated amorphous calcium silicate by ultraviolet excitation at 378 nm. The Tb3+-activated amorphous calcium silicate was prepared by heating a sample of Tb3+-activated calcium silicate hydrate (CSH) at 900°C for 30 minutes. The emission wavelength of the resulting phosphor was 544 nm. The optimum excitation wavelength within the range 300–400 nm was 378 nm. The Tb3+-activated amorphous calcium silicate emitted green by ultraviolet irradiation. The optimum initial Tb/Ca atomic ratio of this phosphor was about 0.5. A mechanism for the action of the phosphor is proposed, in which Tb3+ ions existing in the layer of the CSH lead to loss of water molecules and OH groups.

Luminescence enhancement of LiSrPO4:Eu2+ phosphor by Mg2+ ion addition

Abstract Mg-doped LiSrPO4:Eu2+ (Li(Sr, Mg)PO4:Eu2+) phosphors, in which some Sr2+ ions were replaced by Mg2+ ions, were prepared using a conventional solid-state reaction method. The crystal structure of the phosphors was hexagonal, which is the high-temperature phase of LiSrPO4, even though synthesis was carried out at a relatively low temperature of 900 °C. Fluorescence could be efficiently excited in the 220–400 nm ultraviolet region, and bright blue emission was produced with a peak at 448 nm. The emission intensity was higher than that for LiSrPO4:Eu2+ without Mg doping, and a lower Eu content (1 mol%) was required in order to reach the maximum intensity. These results indicate that the blue-emitting Li(Sr, Mg)PO4:Eu2+ phosphor is a promising candidate for phosphor-conversion white Light Emitting Diodes.

Luminescence Property of Silicate Phosphor, Ba9Sc2Si6O24:Ce, Synthesized by Melt Quenching Technique

Well-grown Ba9Sc2Si6O24:Ce3+ phosphors were synthesized by a novel melt quenching synthesis method. Sintered phosphor balls with excellent luminescent characteristics were obtained. This method is useful tool for rapid screening of phosphor materials.

Luminescence of Phosphor Balls Prepared Using Melt Quenching Synthesis Method

Well-grown M3MgSi2O8(M = Ca, Sr and Ba):Eu2+ phosphors were synthesized by novel melt quenching synthesis method. The luminescence property of the Sr3MgSi2O8:Eu2+ phosphor synthesized by the melt synthesis method is comparable to those of the sample synthesized by a conventional solid state reaction. Sintered phosphor balls with excellent luminescent characteristics were obtained.

Suppress of Concentration Quenching by Site Engineering Concept

Red-emitting RbLa2Ti2TaO10:Eu3+ phosphors were synthesized by a conventional solid-state reaction method, and crystal structure and photoluminescence properties were investigated in the detail. RbLa2Ti2TaO10 has tetragonal structure with a space group of P4/mmm, in which the B-site cations (Ta and Ti) are arranged into non-ordering sequence. The RbLa2Ti2TaO10:Eu3+ phosphors exhibited strong red emission, which is due to the 4f-4f transitions of Eu3+, at excitation wavelength of 396 nm. The concentration quenching phenomena for RbLa2Ti2TaO10:Eu3+ phosphors was investigated using percolation model with two-dimensional interactions among the Eu3+ sites in the host lattice. Both the critical concentration values with the calculation and experiment are estimated to be x = 0.3-0.4, which indicates that the concentration quenching for RbLa2Ti2TaO10:Eu3+ phosphors was due to the energy transfer between the nearest Eu3+ ions in these compounds

Luminescence and Morphology Control of Phosphor Materials Synthesized by Melt Synthesis Method

Efficient and well-grown SrAl2O4:Eu,Dy phosphors were synthesized by an innovative melt synthesis method. The luminescent intensity and after-grow intensity of the SrAl2O4:Eu,Dy phosphors synthesized by the melt synthesis method are comparable to those of the sample synthesized by a conventional solid state reaction. Sintered phosphor balls with excellent luminescent characteristics were obtained.