Blueshift and Photoluminescence Enhancement in Broadband Near‐Infrared Emitting Phosphor NaSr₂(Al/Ga)Ge₅O₁₄: Cr³⁺ Dependence on the Sc/In Substitution

Abstract Cr³⁺‐activated near‐infrared (NIR) phosphors have gained extensive attention for use in NIR phosphor‐converted light‐emitting diodes (pc‐LEDs), which are required for smart NIR spectroscopy techniques. Nevertheless, obtaining broadband NIR‐emitting phosphors with outstanding thermal stabilities and photoluminescence (PL) efficiencies remains a significant challenge. Herein, considering NaSr₂XGe₅O₁₄ (X = Al, Ga, Sc, and In) as hosts, which possess a large band gap and multiple sites for the substitution of Cr³⁺ ions. NaSr₂XGe₅O₁₄:Cr³⁺ phosphors are successfully prepared using a solid‐state reaction technology. Upon blue light excitation, the phosphors cover a broad NIR emission band in 650–1100 nm region. Notably, an abnormal blueshift and PL enhancement are observed following the substitution of Al/Ga with Sc/In. In particular, the PL internal quantum efficiency is improved from 34.5% (NaSr₂GaGe₅O₁₄: Cr³⁺) to 87.5% (NaSr₂ScGe₅O₁₄: Cr³⁺). Moreover, the manufactured NIR pc‐LED exhibited an exceptional photoelectric efficiency of 17.7% with an NIR output power of 10.2 mW at 20 mA, and its potential application in nondestructive detection is demonstrated.