Chromium doped broad-band near-infrared emission Mg4Ta2O9: Cr3+ phosphor excited by blue light for NIR-LEDs

Abstract

Near-infrared light has a wide range of applications in imaging, non-destructive testing, and anti-counterfeiting. Fluorescence conversion method is one of the important methods for making near-infrared (NIR) LED light sources. In this work, we synthesized a novel Cr3+-doped Mg4Ta2O9 system, which can emit NIR light with a peak around 850 nm under the excitation of blue light at 460 nm. It has a broad emission spectrum with full width at half maximum (FWHM) of 178 nm, covering the first NIR region and extending to the second NIR region. The structure, luminescence properties, and applications of this NIR luminescent material have been studied in detail. Cr3+ occupies two six-coordinated Mg2+ sites in this system. The emission spectrum shows an anomalous phenomenon of red-shift with the increase of doping concentration, which is the result of the competition between the crystal field strength and the Jahn-Teller effect. The luminescent material can still maintain 82% of the luminous intensity at 150 °C. By combining with blue InGaN chips, NIR light-emitting optical devices were fabricated, and their potential applications in biological tissue penetration and non-destructive testing were demonstrated.