Near-infrared Sr7NaGa(PO4)6:Cr3+,Ln3+ (Ln = Nd, Er, and Yb) phosphors with different energy transfer paths: photoluminescence enhancement and versatility

Abstract

Near-infrared phosphors are of great interest due to their unique, versatile luminescence properties and exciting application prospects. Herein, a novel broadband emission NIR phosphor Sr₇NaGa(PO₄)₆:Cr³⁺ was synthesized successfully, and photoluminescence properties of the phosphor were studied. When Ln³⁺ ions were co-doped, the photoluminescence was enhanced. Compared with Sr₇NaGa(PO₄)₆:0.15Cr³⁺, the total emission intensity of Sr₇NaGa(PO₄)₆:0.15Cr³⁺,0.15Yb³⁺ increased to 172%, the IQE of Sr₇NaGa(PO₄)₆:0.15Cr³⁺,0.15Nd³⁺ increased from 22 to 72%, and the thermal quenching of Sr₇NaGa(PO₄)₆:0.15Cr³⁺,0.50Er³⁺ suppressed effectively. Highly efficient energy transfer paths are formed in the Sr₇NaGa(PO₄)₆:0.15Cr³⁺,Ln³⁺ phosphors because of the shorter distances between Cr³⁺ ions and Ln³⁺ ions in the Sr₇NaGa(PO₄)₆ host. The energy transfer efficiencies of Cr³⁺ → Ln³⁺ are greater than 70%. Finally, the investigations on night vision, solar cells, and ratiometric luminescent thermometers demonstrate that the as-prepared NIR phosphors have the potential for multifunctional applications.