Origin of the Cr3+ concentration-dependent broadband near-infrared emission in Sc2Si2O7.

The challenge of developing phosphors with tailored near-infrared (NIR) emission ranges to meet the diverse demands of various applications is a paramount concern in the contemporary realm of NIR phosphor research. A strong dependence of NIR emission on Cr⁺³ concentration has been demonstrated in Sc_2-xSi₂O₇:xCr⁺³, which exhibits an NIR emission band at 840 nm for low Cr⁺³ doping concentrations (x = 0.001-0.01) and an anomalous NIR emission band at 1300 nm for high Cr⁺³ doping concentrations (x = 0.01-0.10). Careful investigation of the crystal structure, excitation and emission spectra, and luminescence decay curves indicates that the two NIR emissions can be attributed to the isolated Cr⁺³ ions and the Cr⁺³-Cr⁺³ pairs, respectively. The strong interaction of exchange-coupled Cr⁺³-Cr⁺³ pairs is supported by temperature-dependent emission spectra, luminescence decay curves and electron paramagnetic resonance (EPR) measurements. This work provides a new insight into the study of Cr⁺³-Cr⁺³ pairs for broadband NIR emission. [ABSTRACT FROM AUTHOR]