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

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 4f65d excited state to the 4f7-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 A and 14.9 A 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 (λmax = 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.