Concentration-Driven Selectivity of Energy Transfer Channels and Color Tunability in Ba₃La(PO₄)₃:Tb³⁺, Sm³⁺ for Warm White LEDs

Here, we report the large-scale emission color tunability in Ba₃La­(PO₄)₃:Tb³⁺, Sm³⁺ (BLPO:TS) system based on the detailed discussion on the concentration-driven selectivity of energy transfer (ET) channels from Tb³⁺ to Sm³⁺. It is induced by the concentration-dependent ⁵D₃ and ⁵D₄ emissions of Tb³⁺ and the different interaction mechanisms of ET from Tb³⁺ to Sm³⁺ via ⁵D₃ and ⁵D₄ channels. In the diluted Tb³⁺ scenario, the red emission of Sm³⁺ is efficiently sensitized via the ⁵D₃ channel, while in the concentrated Tb³⁺ case, the contribution of ⁵D₄ channel is dominant. Therefore, by simply adjusting the doping concentrations of Tb³⁺ and Sm³⁺, 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 Tb³⁺, Sm³⁺ coactivated phosphor Ba₃La_0.90Tb_0.05Sm_0.05(PO₄)₃ (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_a ≈ 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 Tb³⁺ and Sm³⁺ activated phosphors.