Single-Crystal Phosphors for High-Brightness White LEDs and LDs(<Special Issue>Recent Advance in Functional Single Crystals)

抄録

White light-emitting diodes (wLEDs) are the new environmental friendly sources for general and specific lighting purposes. Although their commercialization is extending rapidly, current wLEDs cannot be used in applications that require high-brightness due to overheating, which drastically decreases their emission efficiency, color quality and lifetime. This paper reviews the recent investigations on single-crystal phosphors (SCPs) as alternative to conventional ceramic powder phosphors (CPPs). SCPs represent a totally new approach, that can overcome all the difficulties of CPPs. SCPs can realize resin-free, all-inorganic packaging, thus allowing the use of high-power LEDs and LDs. Further, it is demonstrated that in comparison with CPPs, SCPs exhibit an outstanding conversion efficiency and thermal stability up to 300℃. Ce:Y_3Al_5O_<12> SCPs are suitable for neutral white light sources, where a high light intensity is required independently of the color quality. On the other hand, it is shown that Ce:(Y_<1-x>Lu_x)_3Al_5O_<12> SCPs, in combination with an additional red phosphor, are adequate to realize warm and neutral trichromatic white light sources with a color rendering Ra > 90.