Efficient broadband near-infrared emission induced by Nb5+ substitution for Ta5+ in GaTa1-yNbyO4:Cr3+ phosphor

A breakthrough in the luminescence performance of broadband near-infrared (NIR) emitting phosphors is central to their successful application in next-generation smart NIR light sources. Currently, due to the deficiency of phosphors that have both high blue light absorption efficiency (AE) and high NIR internal quantum efficiency (IQE), NIR phosphor-converted LEDs (pc-LEDs) still bear low external quantum efficiencies (EQE) (<40%). In this work, an effective ion substitution strategy, that is Nb5+ substitution for Ta5+, was used to improve the luminescence of GaTaO4(GTO):0.02Cr(3+) phosphor. Consequently, a series of GaTa1-yNbyO4(GTNO):0.02Cr(3+) (y = 0-1.0) solid solution phosphors achieved breakthroughs in the AE, IQE and EQE. Under 474 nm excitation, the AE, IQE and EQE of the GTNO:0.02Cr(3+) (y = 0) phosphor were 39.9%, 75.4% and 30.1%, respectively. After the proper substitution of Nb5+, corresponding to GTNO:0.02Cr(3+) (y = 0.5), the three values were accordingly enhanced to 52.5%, 94.0% and 49.4%, under 476 nm excitation. The ion substitution strategy gave significant breakthroughs in the luminescence efficiency of the NIR phosphors, which is an important guideline for the development of more efficient broadband NIR phosphors in the future.