Narrow-band Rb1−yKyNa3(Li3SiO4)4:Eu2+(0 ≤ y ≤ 1) cyan-blue phosphors for full-spectrum white LEDs

Abstract

A series of Rb_1−yK_yNa₃(Li₃SiO₄)₄:Eu²⁺(0 ≤ y ≤ 1) phosphors were successfully synthesized through a high-temperature solid-state reaction. The introduction of K⁺ into the RbNa₃(Li₃SiO₄)₄:Eu²⁺ phosphor to partially or completely replace Rb⁺ allows the emission spectrum to be modulated from blue (λ = 473 nm, FWHM = 22.5 nm) to a narrow cyan band (λ = 485 nm, FWHM = 21.1 nm). As the K⁺ ion content increases, the space group of the phosphor evolves from I4/M to I41/A. The complete replacement of Rb⁺ by K⁺ results in the KNa₃(Li₃SiO₄)₄:Eu²⁺ cyan phosphor, which shows excellent thermal stability (the comprehensive emission loss is only 8% at 150 °C) and can be used to fill the cyan light gap in white LED devices. By adding the KNa₃(Li₃SiO₄)₄:Eu²⁺ cyan phosphor in packaging with yellow and red phosphors, the color rendering index is increased from 90.2 to 97.1 and the correlated color temperature improved to 3658 K. These results indicate that the cyan phosphor has important application value in full-spectrum white LEDs.