Near-unity quantum efficiency wavelength-tunable NIR phosphors (Sr2−yCay)Sc1−xSbO6: xFe3+ with excellent thermal stability

Fe 3+ ions as near-infrared (NIR) activators are emerging as an alternative to Cr 3+ . 1–5 However, it is a challenge to develop Fe 3+ -activated NIR phosphors featuring tunable optical properties, high efficiency, and thermal stability. Herein, we present a series of near-unity internal quantum efficiency (IQE), wavelength-tunable and thermal stability NIR-emitting phosphors Sr 2− y Ca y Sc 1− x SbO 6 : x Fe 3+ (S 2− y C y S 1− x S: x Fe 3+ ). Sr 2 ScSbO 6 :1%Fe 3+ (SSS:1%Fe 3+ ) phosphor shows broadband NIR emission at 904 nm and near-unity IQE under excitation at 300 nm. Experimental and theoretical calculation results demonstrate that introduced Ca ions could increase the bandgap value and Debye temperature (Θ D ) of host from E g = 3.702 eV, Θ D = 609 K of y = 0 to E g = 3.801 eV, Θ D = 692 K of y = 2. Significantly, the resultant S 2− y C y S 1− x S:1%Fe 3+ NIR phosphors show wavelength-tunable emission from 904 to 952 nm and high IQE of 84.6%–97.5% as well as enhanced thermal stability ( I 423K / I 298K = 76.9%) of Ca 2 ScSbO 6 :1%Fe 3+ (CSS:1%Fe 3+ ) in comparison with that ( I 423K / I 298K = 70.6%) of pristine sample. We fabricated an NIR light-emitting diodes (LED) device by using CSS:1%Fe 3+ NIR phosphors with ultraviolet LED chip and demonstrated its potential applications in anticounterfeiting, information encryption, and night vision.