Energy Transfer in Sr2MgSi2O7:Eu2+ Phosphors in Nano Scale and Their Application to Solid State Lighting with Excellent Color Rendering

Abstract

On the basis of structural information of its host material which shows excellent stability and absorption efficiency in ultra-violet (UV) region, a blue-emitting Sr2MgSi2O7:Eu2+ (SMS:Eu2+) phosphor was synthesized, and its photoluminescence (PL) performance was systematically optimized. In order to enhance its PL properties, Ce3+ was added as a sensitizer based on the energy transfer from the absorption energy of Ce3+ to Eu2+. It was due to the spectral overlap between the photoluminescence excitation spectrum of Ce3+ and the PL spectrum of Eu2+. Moreover, the energy transfer rate from Ce3+ to Eu2+ is generally faster than the emission rate of Ce3+ in the dipole-dipole interaction. Depending upon the amount of Ca2+ substituted into Sr site, their maximum wavelength was varied from similar to 460 to similar to 540 nm in terms of the crystal field effect confirmed by the structural analysis via Rietveld refinement method. Finally, the optimized blue-emitting SMS:Eu2+ and Ca2+-substituted yellowish green-emitting SMS:Eu2+ phosphors were applied with Eu2+-sensitized red-emitting Ca3Mg3(PO4)(4):Mn2+ phosphor introduced in our previous research to UV light emitting diode (LED)-pumped white LEDs. The fabricated white LEDs showed a natural white light with the color coordinate of (0.3298, 0.3280) and the excellent color rendering index of 94.