Energy transfer dynamics in thermally stable single-phase LiMgBO3:Tm3+/Dy3+ phosphor for UV triggered white light-emitting devices

Abstract We report on thermal-, structural-, optical-, and energy transfer (ET)-based photoluminescence (PL) characteristics of Tm3+ co-doped with Dy3+ in a single-phase LiMgBO3 host material. Tm3+ exhibits vibrant blue emission (1D2→3F4: 456 nm) and Dy3+ displays strong yellowish-white emission (4F9/2→6H13/2: 573 nm) under ultraviolet (UV) excitation. When the optimum concentration (0.03) of Tm3+ is co-doped with different amounts of Dy3+, the PL intensity of Tm3+: 1D2→3F4 declines but increases for Dy3+: 4F9/2→6HJ (J = 11/2, 13/2, 15/2), which suggests ET from Tm3+→Dy3+ and demonstrates electric dipole–dipole interaction with a critical distance of 11.07 A. The ET between Tm3+ and Dy3+ is validated from the spectral overlap of Tm3+ PL and Dy3+ absorption, Tm3+/Dy3+ PL spectra, Tm3+-dependent lifetimes, and ET parameters such as efficiency and probability. The Commission Internationale de l’Eclairage (CIE) coordinates display the color tunability of Tm3+ phosphor from blue light (0.146, 0.045) to warm white light (0.334, 0.306) with a correlated color temperature (CCT) value of 5,404 K in response to Dy3+ doping. The PL intensity of LiMgBO3:0.03Tm3+/0.05Dy3+ increases nearly two-fold on co-doping with 5% Li+ as a charge compensator. Tm3+/Dy3+/Li+ co-activated material exhibits good thermal stability, retaining 64% of the initial PL intensity, which suggests its practical applicability as UV light triggered white light-emitting devices.