Color-tunable Al6Si2O13:Eu2+,Mn2+ phosphor with high color rendering index based on energy transfer for warm white LEDs

It is extremely necessary to develop LEDs with a high color index for many special applications. In this study, novel single-phase warm white light-emitting 3/2-mullite (Al6Si2O13):Eu2+,Mn2+ phosphors were prepared via the high-temperature solid-state reaction method. The emission hue can be precisely controlled from (0.2496, 0.3032) to (0.4001, 0.3031) by altering the Eu2+/Mn2+ ratio via the energy transfer route, where warm-white emissions with CIE coordinates of (0.3440, 0.3302) are achieved using UV-excited Al6Si2O13:2.0%Eu2+,0.6%Mn2+ phosphors. The energy transfer between Eu2+ and Mn2+ in the Al6Si2O13 host is demonstrated to be a nonradiative dipole-dipole interaction. A warm-white LED device comprising the Al6Si2O13:2.0%Eu2+,0.6%Mn2+ phosphor and an NUV (365 nm) chip operated at 120 mA yields white-light emissions with a correlated color temperature of 5656 K and color coordinates of (0.3289, 0.3413). Moreover, it should be noted that the color rendering indices of R-a and R9 can reach up to 92.4 and 97.0, respectively. Our proposed Al6Si2O13:2.0%Eu2+,0.6%Mn2+ phosphor with high color rendering index has good application prospects.