A non-rare earth ion doped broadband emission phosphor located in NIR-II for ethanol concentration detection

In this work, a new NIR phosphor Ca₂GeO₄:xCr was developed, whose emission range (1000-1700 nm) is well within NIR-II, with a full width at half maximum (FWHM) of 215 nm. Interestingly, by sintering under an air atmosphere, the Cr³⁺ ions in the raw material are oxidized to Cr⁴⁺, and the near-infrared light emitted by the material is not the usual luminescence of Cr³⁺ ions located in NIR-I, which can be attributed to the dominant substitution of Cr⁴⁺ ions doped into the lattice sites. A pc-LED fabricated with this phosphor can detect different concentrations of ethanol, which demonstrates its good potential for non-destructive testing applications.