Simultaneous realization of tunable luminescence and enhanced thermal stability in Eu2+-based blue-green phosphors for multifunctional applications

Abstract

Developing a new Eu2+-doped blue-green phosphor with tunable spectral in silicate materials is challenging for a high-quality phosphor-converted white light-emitting diode. The cation substitution strategy is a valid way to concurrently modify spectral characteristics and optimize luminescence performances. Herein, a series of NaBaScxLu1-xSi2O7: Eu2+ phosphors with blue-green color-tunable luminescence have been designed. By modulating the ratio of Sc/Lu, controllable regulation of the photoluminescence and thermal stability properties can be realized simultaneously. Moreover, the initial emission intensity is monotonically increased by 2.92 times and the quantum efficiency is enhanced dramatically by introducing Sc3+. Especially, the thermal stability is boosted from 53.4% to 90.9% and the emission shifted from 485 to 504 nm is improved due to the chemical substitution of Sc in the Lu site with the lattice shrinks resulting in the Eu5d energy level farther away from the conduction band and a minimum 5d energy level closer to the ground state energy level. Furthermore, the fabricated w-LEDs with NaBaScxLu1-xSi2O7: Eu2+ blue-green phosphors and (Sr, Ba)3SiO5: Eu2+ red phosphor exhibit a high color rendering index (Ra = 87.2) and desired color-dependent temperature (CCT = 3711 K). Except for the application in solid-state illumination, the potential application of synthetic phosphors in optical anti-counterfeiting is also explored. The luminescence tunable strategy via cation substitutions simultaneously modifies emission and improves thermal stability, providing a distinctive design philosophy for the development of Eu2+-doped silicate phosphors.