Enhancing the luminescence performance of an LED-pumped Mn4+-activated highly efficient double perovskite phosphor with A-site defects via local lattice tuning

Abstract

Altering the local symmetry of an activator by lattice tuning is considered an effective strategy to optimize the luminescence performance of phosphors. Herein, the novel Mn⁴⁺-activated double perovskite phosphor La_1.67MgTaO₆ (LMTO) with A-site defects was successfully prepared. Benefiting from the random occupation of the nearest A-site by cations and vacancies, the distorted [MnO₆] octahedra lack the inversion center. The LMTO:0.4 mol%Mn⁴⁺ phosphor has a significant zero-phonon line intensity with a high internal quantum efficiency (IQE) value of 62.97% after the Laporte selection rule is broken. Furthermore, local lattice tuning was performed by increasing the randomness of the A-site and the distortion index of the [MnO₆] octahedron by co-doping with Ca²⁺ or Sr²⁺ ions. Importantly, the IQE value of the samples was enhanced from 62.97% to 72.65% and the activation energy increased from 0.497 eV to 0.548 eV, which can be well applied in the fields of plant cultivation and warm white light-emitting diodes. These studies provide valid fundamental insights for the selection of excellent luminescent matrices to obtain efficient Mn⁴⁺-activated phosphors via local lattice tuning.