The effects of Lu3+, Gd3+ and Ga3+ substitution on the photoluminescence of Y2.95−x−yLuxGdyAlzGa5−zO12:0.05Ce3+ phosphors for high-power white AC-LEDs

Abstract

Various yellowish-green persistent phosphors of Y_2.95−x−yLu_xGd_yAl_5−zGa_zO₁₂:0.05Ce³⁺ (x = 0–1, y = 0–1, z = 1–4) were successfully synthesized by the one-step high-temperature solid-state reaction method in air. The effects of simultaneous doping of Lu³⁺, Gd³⁺ and Ga³⁺ on the luminescence properties of the phosphors were investigated in detail for the first time. Herein, the microstructure, morphology, afterglow performance, luminescence properties, thermoluminescence, thermal quenching and flicker index of the efficient blue-light-activated Y_2.95−x−yLu_xGd_yAl_5−zGa_zO₁₂:0.05Ce³⁺ phosphors were tested. The τ₉₀ and τ₈₀ values of Y_1.45LuGd_0.5Al_2.5Ga_2.5O₁₂:0.05Ce³⁺ are 10.8 ms and 33.2 ms, respectively. These parameters are important in terms of effectiveness in reducing flicker in alternating current (AC) LEDs. Compared with the conventional Y₃Al₂Ga₃O₁₂:Ce³⁺ phosphor, the Y_1.45LuGd_0.5Al_2.5Ga_2.5O₁₂:0.05Ce³⁺ phosphor has a better luminescence performance, stronger afterglow performance, and lower flicker index. The quantum yield of the Y_1.45LuGd_0.5Al_2.5Ga_2.5O₁₂:0.05Ce³⁺ phosphor was 86.42% and the luminous efficiency of the LED devices prepared with it reached 92.12 lm W⁻¹ when operated at 100 mA. Integrating sphere and spectroradiometer tests as well as CIE chromaticity diagrams indicate that the AC-WLEDs assembled by mixing the Y_1.45LuGd_0.5Al_2.5Ga_2.5O₁₂:0.05Ce³⁺ phosphor and a commercial red phosphor in an appropriate ratio could obtain ideal white light with a high color-rendering index (87.9) and the flickering index was successfully reduced from 100% to 61.4%.