Defect induced visible-light-activated near-infrared emissions in Gd_(3-x-Y-z)Yb_xBi_yEr_zGa_5O_(12)

摘要

Visible-light-activated near-infrared luminescent materials are promising photoluminescent materials due to their convenience and low cost. Crystal defects can seriously affect the performance of luminescent materials, and better understanding of the complexity of the structural disorder and electronic structures of such materials opens up new possibilities in luminescent material development. In this work, we successfully design a novel, effective, visible-light-activated near-infrared luminescent Gd_3Ga_5O_(12): 4.2%Yb~(3+), 8.4%Er~(3+), and 4.2%Bi~(3+) system based on first principles. This exhibits strong emission intensity and high luminous efficiency (0.993) and also has a lifetime (7.002 ms) that is at least twice as long as the longest lifetime reported in published papers. We utilize density functional theory with an effective LSDA + U method to study the structural properties of Gd_(3-x-y-z)Ga_5O_(12): xYb~(3+), yBi~(3+), zEr~(3+) (GGG: Yb~(3+), Bi~(3+), Er~(3+)). The d and f electron orbits of rare-earth ions are considered for an effective Hund exchange. Detailed analysis reveals that GGG: 4.2%Yb~(3+), 8.4%Er~(3+), 4.2%Bi~(3+) has the smallest cell volume because of the strong covalent bonds of Bi-O, Er-O, and Yb-O. Bi 3d is a hybridized state that acts as sensitizing ions during the process of luminescence in GGG: Yb~(3+), Bi~(3+), Er~(3+). Together with experimental and theoretical results, we analyze the influence of defects on emission intensity. The locations of Yb~(3+), Er~(3+), and Bi~(3+) are determined by X-ray absorption fine structure measurements, which are in agreement with the model constructed using first principles. This work may provide innovative guidance for the design of high-performance visible-light-activated near-infrared luminophores based on calculations and a new methodology for application of coherent laser radar and optical communication.