Tunable luminescent spectra via energy transfers between different lattice sites in Ce³⁺, Mn²⁺ codoped Ba₉Lu₂Si₆O₂₄ phosphors for NUV-based warm white LED applications

A series of Ce³⁺–Mn²⁺ codoped Ba₉Lu₂Si₆O₂₄ (BLS) were synthesized by high-temperature solid-state reactions. The 380–410 nm excitation band of Ce³⁺ at the Lu sites (Ce(1)) matches well with the emission light of commercial near-ultraviolet (NUV) light-emitting diode (LED) chips. Under the Ce(1) excitation, BLS:Ce³⁺, Mn²⁺ exhibited a tunable emission from blue–green to yellow–orange via energy transfers (ETs) from Ce(1) to Mn²⁺. The ET was demonstrated to be of the resonant type via a dipole–quadrupole mechanism. At room temperature (RT), the optimal internal and external quantum efficiencies (QEs) of BLS:Ce³⁺, Mn²⁺ were determined as 79 and 42%. At 150 °C, 85% of the RT QE still can be remained, showing a high thermal stability. A warm white LED (WLED) with a color rendering index of 84 and a correlated color temperature of 3660 K was obtained by combining a 395 nm NUV chip with the phosphor and CaAlSiN₃:Eu²⁺. The efficiency reaches 17 lm W⁻¹ at 20 mA, which is better than the value of most NUV-based WLEDs. These results indicate the promising application of the phosphor as an attractive candidate for WLEDs.