Evaluating Ce³⁺ → Tb³⁺ → Eu³⁺ cascade sensitization in LiSrY₂(BO₃)₃ for near-UV excited white emission

Phosphor-converted white light-emitting diodes (pc-WLEDs) based on near-ultraviolet (NUV) excitation require single-phase phosphors that can simultaneously balance efficient energy transfer and well-distributed multi-colour emission. Although Ce³⁺/Tb³⁺/Eu³⁺ co-doping has been widely explored across various host lattices as a general strategy for white-light generation, its success strongly depends on the host lattice, which must simultaneously satisfy suitable excitation matching, efficient energy transfer, and good thermal stability. In this work, the borate host LiSrY₂(BO₃)₃ (LSYB), which crystallizes in the trigonal space group P3̄m1, is investigated as a host lattice for evaluating cascade sensitization. Benefiting from the broad NUV absorption and small Stokes shift of Ce³⁺, together with the previously identified Tb³⁺ → Eu³⁺ energy transfer in this host, the feasibility of constructing a Ce³⁺ → Tb³⁺ → Eu³⁺ cascade pathway is rationally evaluated. Photoluminescence spectra and lifetime analyses confirm efficient Ce³⁺ → Tb³⁺ and Tb³⁺ → Eu³⁺ energy transfer processes, enabling stepwise spectral evolution from blue to green and ultimately to white light upon Eu³⁺ incorporation. An optimized composition, LiSr(Y_0.978Ce_0.007Tb_0.005Eu_0.01)₂(BO₃)₃, exhibits near-white emission with CIE coordinates of (0.3030, 0.3351) under 335 nm excitation and a correlated color temperature of 6989 K. The phosphor retains 60.47% of its emission intensity at 423 K, indicating good thermal stability. This work demonstrates that LSYB is a suitable host for Ce³⁺-sensitized cascade energy transfer, providing insight into host-dependent design of single-phase white-emitting phosphors, particularly in balancing cascade energy transfer and luminescence efficiency.