Among rare-earth ions, Dy3+ uniquely enables intrinsic white-light emission and is therefore considered a promising activator for solid-state lighting. However, its parity-forbidden 4f–4f transitions lead to intrinsically weak absorption and limited emission intensity. Ce3+ was identified as an efficient sensitizer in the host LiSrY2(BO3)3 (LSYB) to enhance Dy3+ emission through energy transfer. A series of Ce3+-singly doped, Dy3+-singly doped, and Ce3+/Dy3+ codoped phosphors were successfully synthesized via a high-temperature solid-state reaction. Under 347 nm excitation, Dy3+-doped samples exhibit pale yellow emission with yellow-to-blue intensity ratios of 1.15–1.26, indicating that Dy3+ occupies noncentrosymmetric sites. The Dy3+-only phosphor shows relatively low internal quantum efficiency (IQE = 15.47%) and external quantum efficiency (EQE = 1.29%). Upon Ce3+ sensitization, the emission intensity of Dy3+ is significantly enhanced. The optimized codoped phosphor LiSr(Y0.97Ce0.01Dy0.02)2(BO3)3 achieves a markedly improved EQE of 6.10% under 335 nm excitation, with the Dy3+ contribution reaching 3.07%. The Ce3+ emission lifetime decreases with increasing Dy3+ concentration, confirming the occurrence of Ce3+ → Dy3+ energy transfer, which is dominated by an electric dipole–dipole interaction mechanism. LiSr(Y0.96Ce0.01Dy0.03)2(BO3)3 exhibits near-ideal white emission with CIE coordinates of (0.3288, 0.3479), CCT = 5654 K, Ra = 67. Furthermore, the optimized white-emitting phosphor exhibits remarkable thermal stability, maintaining 93.88% of its emission intensity at 423 K relative to that at room temperature.
Chen et al. (Fri,) studied this question.