Bredigite-structure orthosilicate phosphor as a green component for white LED: the structural and optical properties

Abstract

A green-emitting phosphor, Ca14-xEuxMg2[SiO4](8) (CMS:Eu2+), has been synthesized as a component of white light emitting diodes (WLEDs). The emission spectrum is broad, with a maximum at about 505 nm under 400 nm excitation due to the transition from the 4 f(6) 5d excited state to the 4 f(7)-ground state of a Eu2+ ion. The dipole-dipole interaction was a dominant energy transfer mechanism of the electric multipolar character of CMS:Eu2+. The critical distance was calculated as 12.9 angstrom and 14.9 angstrom using a critical concentration of Eu2+ and Dexter's theory for energy transfer. When CMS:Eu2+ and red phosphor are incorporated with an encapsulant on an ultraviolet (lambda(max) = 395 nm) light emitting diodes (LEDs), white light with a color rendering index of 91 under a forward bias current of 20 mA was obtained. The structural and optical characterization of the phosphor is described. (C) 2012 Optical Society of America