Highly efficient broadband near-infrared-emitting (Sr,Ba)3ZnTa2O9:Cr3+ phosphors based on crystal-field engineering toward veins imaging and night vision applications

The development of near-infrared (NIR) spectroscopy technology has led to enormous research on NIR radiation sources, which urgently calls for the discovery of novel tunable broadband NIR-emitting phosphors. In the present work, substantially regulatable NIR luminescence is firstly realized in the perovskite-like (Sr1-yBay)(3)ZnTa2O9:Cr3+ (S(1-y)B(y)ZTO:Cr3+) phosphors based on the crystal-field engineering strategy. The regular [ZnO6] and distorted [TaO6] octahedra establish the three-dimensional structural framework of the S(1-y)B(y)ZTO host lattice by connecting with O atoms, in which the Sr/Ba site resides via constructing the [(Sr/Ba)O-12] decahedron. The initial component SZTO:Cr3+ possesses the broadband emission bands distributed in the NIR-I spectral region and exhibits high internal quantum efficiency (IQE, IQE = 80.9 %) and desirable thermal stability (I-473 K/I-298 K = 77.6 %), overwhelming most of other recently emerging Cr3+-doped NIR-emitting phosphors. While maintaining the above superb features of SZTO:Cr3+, Ba2+/Sr2+ substitution in S(1-y)B(y)ZTO:Cr3+ is further utilized to achieve substantially regulatable NIR luminescence with the red-shifted emission from 800 to 856 nm, which is attributed to the weakened crystal field environment of Cr3+, theoretically verified according to the Tanabe-Sugano diagram. A fabricated NIR phosphor-converted light-emitting diode prototype coated with the representative S(0.6)B(0.4)ZTO:0.01Cr(3+) phosphor finally provides ideal NIR output with desirable luminous efficacy of 68.6 lm/W, showing the applicable potential for veins imaging and night vision. Guided by the crystal-field engineering strategy via alkaline-earth metal cationic substitution, these findings provide an effective approach to achieving the excellent luminescence performance in the novel phosphor systems, which is conducive to stimulating relevant studies on the tunable broadband NIR-emitting phosphors for further applications.