Phosphors for White LEDs in the Next Stage

This paper reviews physical pictures of phosphor materials, which can meet requirements of diversified white-LED applications in the next stage. Suppression of thermal quenching and suitable band width of luminescence are the main concern. Basically tight space around an emitting ion and rigid chemical bonding can improve thermal quenching and narrow the band width. There are, however, other factors such as delocalization of an excited state leading to nanradiative processes. Preferable properties are discussed with reference to examples, e.g. La_2O_2S:Eu^<3+>, Y_3Al_5O_<12>:Ce^<3+> and CaAlSiN_3:Eu^<2+>, which show a difference in quenching temperature and β-SiAlON:Eu^<2+>, which has a narrow band width.