A novel phosphor for glareless white light-emitting diodes.
The luminous efficiency of white light-emitting diodes, which are used as light sources for next-generation illumination, is continuously improving. Presently available white light-emitting diodes emit with extremely high luminance because their emission areas are much smaller than those of conventional light sources. Consequently, white light-emitting diodes produce a glare that is uncomfortable to the human eye. Here we report a yellow-emitting phosphor, the Eu(2+)-doped chlorometasilicate (Ca(1-x-y,)Sr(x,)Eu(y))(7)(SiO(3))(6)Cl(2), which can be used to create glareless white light-emitting diodes. The (Ca(1-x-y,)Sr(x,)Eu(y))(7)(SiO(3))(6)Cl(2) exhibits a large Stokes shift, efficiently converting violet excitation light to yellow luminescence, and phosphors based on this host material have much less blue absorption than other phosphors. We used crystal structure analysis to determine the origin of the desired luminescence, and we used (Ca(1-x-y,)Sr(x,)Eu(y))(7)(SiO(3))(6)Cl(2) and a blue-emitting phosphor in combination with a violet chip to fabricate glareless white light-emitting diodes that have large emission areas and are suitable for general illumination.
Department of Research and Development, Koito Manufacturing Co., Ltd, Shizuoka 424-8764, Japan. hdaicho@koito.co.jp
Hisayoshi
H
Daicho
Takeshi
T
Iwasaki
Kiminori
K
Enomoto
Yasutaka
Y
Sasaki
Yuzo
Y
Maeno
Yu
Y
Shinomiya
Shinobu
S
Aoyagi
Eiji
E
Nishibori
Makoto
M
Sakata
Hiroshi
H
Sawa
Satoru
S
Matsuishi
Hideo
H
Hosono
D018360:Crystallography, X-Ray; D004581:Electronics; D005063:Europium / Q000737:chemistry; D006801:Humans; D008027:Light; D049449:Luminescence; D049408:Luminescent Agents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014785:Vision, Ocular
D049408:Luminescent Agents; D005063:Europium