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

Highlights: • Single-phase LiMgBO₃:Tm³⁺/Dy³⁺ phosphors were synthesized by solid-state reaction method. • Quenching of Tm³⁺ emission and lifetime in the presence of Dy³⁺ demonstrates the ET from Tm³⁺→Dy³⁺ governed by dipole–dipole interaction. • The PL intensity of LiMgBO₃:Tm³⁺/Dy³⁺ exhibited nearly two-fold enhancement upon co-doping with 5% Li⁺ as a charge compensator. • The Color tunability from blue to white demonstrates the applicability of LiMgBO₃:Tm³⁺/Dy³⁺ as a white light phosphor in white LEDs. 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 (⁴F_9/2→⁶H_13/2: 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⁺: ⁴F_9/2→⁶H_J (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 Å. 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.