Ultra-Broadband Near-Infrared Phosphors Realized by the Heterovalent Substitution Strategy

Abstract

Near-infrared (NIR) phosphor-converted light-emitting diodes with broadband emission have received considerable interest. However, there remains a challenge in the construction of ultra-broadband NIR phosphors, hindering their further application. In this work, a heterovalent substitution strategy is proposed to construct a novel ultra-broadband NIR-emitting LaTiTaO₆:Cr³⁺ phosphor with a full width at half maximum of ∼300 nm. Crystal structure, time-resolved emission spectroscopy, and electron paramagnetic resonance analyses confirm that only one crystallographic site of Cr³⁺ with separated ions exists. Electron and phonon coupling (EPC) evaluated by the Huang-Rhys factor (<i>S</i>) reveals that the heterovalent substitution strategy contributes to strong EPC with <i>S</i> = 9.185, resulting in ultra-broadband emission. Interestingly, a remarkable blue shift of emission from 1050 to 922 nm with increasing temperature is observed. Moreover, the application of LaTiTaO₆:Cr³⁺ phosphor is demonstrated in the qualitative analysis of ethanol/water mixtures. The work will enrich the toolbox for designing broadband NIR-emitting materials.