Room-Temperature Synthesis of Highly-Efficient Eu³⁺-Activated KGd₂F₇ Red-Emitting Nanoparticles for White...

Luminescent materials with high thermal stability and quantum efficiency are extensively desired for indoor illumination. In this research, a series of Eu³⁺-activated KGd₂F₇ red-emitting nanoparticles were prepared at room temperature and their phase structure, morphology, luminescence properties, as well as thermal stability, have been studied in detail. Excited by 393 nm, the resultant nanoparticles emitted bright red emissions and its optimal status was realized when the Eu³⁺ content was 30 mol%, in which the concentration quenching mechanism was triggered by electric dipole-dipole interaction. Through theoretical analysis via the Judd-Ofelt theory, one knows that Eu³⁺ situates at the high symmetry sites in as-prepared nanoparticles. Moreover, the internal and extra quantum efficiencies of designed nanoparticles were dependent on Eu³⁺ content. Furthermore, the studied nanoparticles also had splendid thermal stability and the corresponding activation energy was 0.18 eV. Additionally, via employing the designed nanoparticles as red-emitting constituents, a warm white light-emitting diode (white-LED), which exhibits low correlated color temperature (4456 K), proper luminous efficiency (17.2 lm/W) and high color rendering index (88.3), was developed. Our findings illustrate that Eu³⁺-activated KGd₂F₇ nanoparticles with bright red emissions are able to be used to promote the performance of white-LED.