Bi³⁺-sensitized Dy³⁺ emission for tunable luminescence and efficiency enhancement in LiY₆O₅(BO₃)₃ phosphors

Dy³⁺ is a rare-earth ion with the potential to emit white light, making it attractive for solid-state lighting applications. However, its inherently low luminescence efficiency, resulting from parity-forbidden 4f-4f transitions, limits its practical use. To overcome this challenge, sensitization strategies using Bi³⁺ have been proposed to enhance Dy³⁺ emission. In this study, a series of high-purity Li(Y_1-<i>x</i>Dy_<i>x</i>)₆O₅(BO₃)₃ (0.01 ≤ <i>x</i> ≤ 0.05) and Li(Y_{0.99-<i>y</i>}Bi_0.01Dy_<i>y</i>)₆O₅(BO₃)₃ (0.01 ≤ <i>y</i> ≤ 0.05) samples were synthesized <i>via</i> a high-temperature solid-state reaction method. The successful incorporation of dopant ions into the host lattice was confirmed by linear changes in unit cell volume derived from Le Bail fitting of PXRD data. The optimized Dy³⁺-singly doped sample (<i>x</i> = 0.02) exhibited a yellowish emission with an IQE of 12.0%. Upon Bi³⁺ co-doping, energy transfer from Bi³⁺ to Dy³⁺ was realized, resulting in a threefold enhancement in Dy³⁺ emission intensity. The co-doped phosphor Li(Y_0.98Bi_0.01Dy_0.01)₆O₅(BO₃)₃ achieved an IQE of 43.3% under 302 nm excitation. The energy transfer mechanism was identified as electric dipole-quadrupole interaction based on lifetime analysis. Additionally, tunable emission from blue to purplish-white was achieved by adjusting the Bi³⁺/Dy³⁺ ratio. These results demonstrate the potential of LYBO as an efficient host for Bi³⁺-sensitized Dy³⁺ phosphors and provide a valuable reference for the future design of rare-earth-doped luminescent materials for customizable white light emission.