(a) PL spectra of a series of BPO:0.01Ce³⁺, yTb³⁺ (y = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, and 0.10) under 315-nm excitation; (b) the intensity of Ce³⁺ at 348 nm and Tb³⁺ at 545 nm varying with Tb³⁺ doping concentration; (c) decay curve of BPO:0.01Ce³⁺, yTb³⁺ (x = 0.00–0.10) recorded under 290-nm nano-LED light; (d) luminescence lifetime of Ce³⁺ and energy transfer efficiency varying with doped Tb³⁺ ion concentration.