Novel broadband near-infrared emission in Cr3+-activated Sr3ZnGe5O14 phosphor for an electroluminescent stable pc-LED

Near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have exhibited tremendous potential in spectroscopic technology, promoting the demand of developing novel NIR materials with excellent properties. In this paper, a series of germanate based NIR phosphors Sr3ZnGe5O14: xCr3+ (0 <= x <= 0.05) were synthesized by high temperature solid state reaction. The X-ray diffraction (XRD), scanning electron microscopy (SEM), Ultraviolet diffuse reflection, photoluminescence spectra and PL decay were measured to analyze the crystal structure, morphology properties and elements composition, PL emission properties and lifetimes of these NIR phosphors. Results demonstrated that phosphors Sr3ZnGe5O14: xCr3+ (0 <= x <= 0.05) crystallized in a trigonal with a space group of P321(150) with a broad band gap (Eg) of 4.70-4.59 eV. Sample Sr3ZnGe5O14: 0.03Cr3+ with the best PL emission properties showed a good thermal stability with the PL emission intensity remains 69 % of its initial value at 420 K. It's worth noting that the NIR device based on Sr3ZnGe5O14: 0.03Cr3+ displays an impressive electroluminescent emission stability, for example, the electroluminescent emission intensity is still about 92.3 % of its initial value when the NIR pc-LED light up for 18 h. These research results provided an important guidance for developing novel Cr3+ doped germanate based NIR phosphors with excellent thermal and electroluminescent emission stability.