Achievement of high efficiency and thermally stable near-infrared phosphors by designing a chromium crystallographic environment for nondestructive testing and night vision

Abstract

Clarification of the effect of the crystallographic environment of Cr³⁺ ions on its luminescence properties is essential for the construction of novel stable and efficient near-infrared (NIR) phosphors. To this end, we investigated a series of XTaO₄:Cr³⁺ (X = In, Sc, and Ga) phosphors with Cr³⁺ ions occupying the [XO₆] crystallographic sites. And the thermal stability increased from 8% to 73% and the IQE increased from 36% to 82.6% when X changed from In to Ga. An analysis of the internal reasons for the dramatic changes in the luminescence properties caused by Cr³⁺ ions occupying different crystallographic site environments has been performed in detail. With the order of X = In, Sc, and Ga, the Debye temperature of XTaO₄:Cr³⁺ was significantly enhanced and the electron–phonon coupling effect was gradually reduced, and as a result, GaTaO₄:Cr³⁺ with desirable structural rigidity has a high internal/external quantum efficiency (IQE/EQE: 82.6%/43.5%) and good thermal stability (I_423K = 73%). Finally, NIR phosphor-converted light-emitting diodes (pc-LEDs) were fabricated by combining XTaO₄:Cr³⁺ (X = In, Sc, and Ga) with blue LED chips and demonstrated for applications in nondestructive testing and night vision. The results provide a novel pointcut for the design of NIR light-emitting materials with desirable luminescence properties.