A highly thermal stable cubic-phase Sc(PO3)3:Cr3+ phosphor with emitting peak at 875 nm

The compact size and high efficiency of near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) make them promising light sources in various fields, such as miniature NIR spectrometer. However, the current state of NIR phosphors with emission wavelengths exceeding 850 nm shows poor photoluminescence (PL) thermal stability. In this work, we present cubic-phase Sc(PO3)3:xCr3+ (x = 0, 1, 5, 10, 12, 14, 16 and 18 at%) phosphors that exhibit broadband emission ranging from 725 to 1150 nm, with a peak at 875 nm. Particularly, the PL intensity of the 5 at% sample retains 73.4% of its value at room temperature when measured at 423 K, exhibiting exceptional thermal stability compared with previously reported phosphors with emission peaks exceeding 850 nm. Through a comparison investigation on the variable-temperature X-ray diffraction patterns of cubic- and monoclinic-phase Sc(PO3)3:Cr3+ phosphors, it was revealed that achieving good PL thermal stability in the cubic-phase phosphor may be attributed to the minimal bond length and bond angle variations at elevated temperatures. The fabricated NIR pc-LEDs, driven with a 150-mA current, produce an NIR radiant flux of 26.62 mW. The highest electro-optical conversion efficiency is 11.87% under a drive current of 10 mA. This work provides insights for the discovery of Cr3+ ion-doped NIR phosphors with excellent PL thermal stability.