A Cr3+-Yb3+ co-doped high-efficiency near-infrared luminescent phosphor for NIR-II light source applications

Phosphor conversion light-emitting diode (PC-LED) technology has become a focal point of research for portable near-infrared light sources in recent years. One of the crucial aspects is to develop phosphor materials that can be effectively stimulated by commercial available blue light. Unfortunately, efficient phosphors in the NIR-II that can be excited by commercial blue light are particularly scarce. In this study, Mg ₄Ta ₂O ₉:0.04Cr ³⁺,0.03Yb ³⁺,0.07Li ⁺ (MTO:0.04Cr ³⁺,0.03Yb ³⁺,0.07Li ⁺) phosphor was synthesized using the high temperature solid phase method, and its emission spectrum covered the first and second near-infrared windows (700–1200 nm). The internal quantum efficiency (IQE) and external quantum efficiency (EQE) are 88.7 % and 45.6 %, respectively, due to the synergistic effect of energy transfer and Li-ion modification. Additionally, the doping of Yb ³⁺ ions and Li ⁺ ions enhances the thermal stability of luminescence. The thermal stability of MTO:0.04Cr ³⁺,0.03Yb ³⁺,0.07Li ⁺ and MTO:0.04Cr ³⁺,0.03Yb ³⁺ is 9.81 % and 14.43 % higher, respectively, than that of MTO:0.04Cr ³⁺,0.03Yb ³⁺ and MTO:0.04Cr ³⁺. To evaluate its potential applications, we developed a prototype PC-LED utilizing MTO:0.04Cr ³⁺,0.03Yb ³⁺,0.07Li ⁺ phosphor as an emission emitter which demonstrated advantages in biomedical imaging, night vision, and non-destructive testing.