Illumination consumes no electricity

While bright, long-duration phosphorescence has been achieved in the violet-to-green wavelength range with rare-earth-doped strontium aluminum oxides, attempts to achieve orange-to-red phosphorescence using various metal-doped oxides have produced results inferior in brightness and afterglow duration.

May 1st, 2007
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While bright, long-duration phosphorescence has been achieved in the violet-to-green wavelength range with rare-earth-doped strontium aluminum oxides, attempts to achieve orange-to-red phosphorescence using various metal-doped oxides have produced results inferior in brightness and afterglow duration. But researchers at Ryukoku University (Otsu, Japan) have demonstrated conversion of weak phosphorescence to efficient strong fluorescence of a different color using a different approach-downconversion of organic dyes-and have now fabricated acrylic resins that yield bright illumination across the entire visible spectral range without consuming electricity.

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To fabricate the resins, phosphor particles and dye molecules were suspended in a photocurable acrylate matrix and solidified. Depending upon the phosphor and dye molecule concentrations, emission of color across the visible spectrum could be obtained after exposure to a white-light source. Upon removal of the light source, illumination decayed from approximately 1 nW/mm2 to around 0.01 nW/mm2 after one hour. Optical power of the red emission-obtained by mixing blue and green phosphors with red organic dye-measured 90 minutes after the excitation source was turned off was found to be seven times higher than that of conventional red phosphors. Contact Mitsunori Saito at msaito@rins.ryukoku.ac.jp.

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