Investigation of the luminescence properties and energy transfer mechanisms in Gd3TaO7:Bi3+,Eu3+ phosphors for their potential application in full-spectrum WLEDs

Abstract

In recent years, there has been increasing effort devoted to the development of single-phase white phosphors due to drawbacks such as severe reabsorption and color deviation in traditional white light-emitting diodes (WLEDs). A new feasible strategy has emerged for achieving white light emission through the Bi³⁺-Eu³⁺ energy transfer in suitable single-phase phosphors. Therefore, a series of Gd₃TaO₇:xBi³⁺ and Gd₃TaO₇:0.01Bi³⁺,yEu³⁺ phosphors were synthesized via a high-temperature solid-state method, and their properties were systematically characterized. In Gd₃TaO₇, Bi³⁺ occupies two kinds of Gd³⁺ site, resulting in two broad emission bands peaking at 427 nm and 500 nm respectively under ultraviolet (UV) excitation, which arise from ³P₁ → ¹S₀ transitions. By adjusting the concentration of Eu³⁺ in Gd₃TaO₇:0.01Bi³⁺,yEu³⁺, effective energy transfer can occur between Bi³⁺ and Eu³⁺, thus enabling the regulation of green-white-red luminescence under 332 nm excitation and blue-white-red luminescence under 365 nm UV light irradiation. Upon stimulation with a 365 nm UV chip, Gd₃TaO₇:0.01Bi³⁺,0.02Eu³⁺ emits white light with CIE coordinates of (0.3509, 0.3202), a color temperature of 4629 K, and an impressive color rendering index of 87.96. The above results indicate the potential of Gd₃TaO₇:0.01Bi³⁺,yEu³⁺ phosphor as a viable candidate for WLED applications.