The ultra-wideband near-infrared luminescence properties and applications of K2SrGe8O18:Cr3+ phosphor

Abstract

The near-infrared (NIR) light sources are fascinating in real-time nondestructive examination applications. Given that chemical bonds in organic substances (such as C–H, O–H and N–H) have extensive absorption and reflection of light in the NIR region, the emission spectrum of the NIR light sources should be as broad as possible. In this work, ultra-wideband K2SrGe8O18 (KSGO):Cr3+ NIR-emitting phosphors with a 650–1200 nm emission span are developed. Structural analysis combined with electron paramagnetic resonance (EPR), photoluminescence (PL) spectra, time-resolved spectrum (TRES) and temperature-dependent PL spectra confirm that the super broadband emission with full width at half-maximum (FWHM) of 214 nm originates from the double Cr3+ luminescence centers occupying different [GeO6] octahedra. Li+ ion as charge compensator is introduced to balance the negative charge induced by the un-equivalent replacement of Cr3+ for Ge4+, and the PL intensity and thermal stability are greatly enhanced. The NIR phosphor-converted luminescent diodes (pc-LEDs) prepared by combining optimized KSGO:0.10Cr3+, 0.07Li+ samples with 460 nm LED chips demonstrate their application in night vision. The measured absorption spectra of hemoglobin, water, ethyl alcohol and peanut oil illuminated by the as-prepared KSGO:0.10Cr3+, 0.07Li+ phosphors indicate nondestructive analysis in the areas of food safety.