Concentration-Driven Selectivity of Energy Transfer Channels and Color Tunability in BaLa(PO):Tb, Sm for Warm White LEDs.

Here, we report the large-scale emission color tunability in BaLa(PO):Tb, Sm (BLPO:TS) system based on the detailed discussion on the concentration-driven selectivity of energy transfer (ET) channels from Tb to Sm. It is induced by the concentration-dependent D and D emissions of Tb and the different interaction mechanisms of ET from Tb to Sm via D and D channels. In the diluted Tb scenario, the red emission of Sm is efficiently sensitized via the D channel, while in the concentrated Tb case, the contribution of D channel is dominant. Therefore, by simply adjusting the doping concentrations of Tb and Sm, the emission color of the phosphors can be tuned from green to red. In view of the phosphors with red emissions are critical to the warm white light-emitting diodes (WLEDs), an orange-red Tb, Sm coactivated phosphor BaLaTbSm(PO) (BLPO:5T5S) with good thermal and chromaticity stability and internal quantum efficiency ∼67% is developed in the system. Then, a near-UV WLED (CCT ≈ 4500 K, R ≈ 81) is fabricated using this phosphor. These findings not only indicate that the orange-red phosphor BLPO:5T5S is available for near-UV warm white LEDs but also deliver new insights into the ET processes in Tb and Sm activated phosphors.