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

Abstract

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 Cr³⁺ concentration has been demonstrated in Sc_2−xSi₂O₇:xCr³⁺, which exhibits an NIR emission band at 840 nm for low Cr³⁺ doping concentrations (x = 0.001–0.01) and an anomalous NIR emission band at 1300 nm for high Cr³⁺ 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 Cr³⁺ ions and the Cr³⁺–Cr³⁺ pairs, respectively. The strong interaction of exchange-coupled Cr³⁺–Cr³⁺ 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 Cr³⁺–Cr³⁺ pairs for broadband NIR emission.