Efficient and Thermally Robust Broadband Near‐Infrared Emission in a Garnet Ca3MgHfGe3O12:Cr3+ Phosphor

Abstract Near‐infrared (NIR) spectroscopy based on phosphor‐converted light‐emitting‐diode (pc‐LED) has promising applications in food quality analysis, security monitoring, medical diagnosis, and bioimaging fields, stimulating the demand of developing NIR phosphors with high‐performance. Herein, a highly efficient and thermally robust Ca 3 MgHfGe 3 O 12 :Cr 3+ NIR phosphor is discovered, which exhibits a broadband NIR emission (λ em = 800 nm) covering 700 to 1100 nm region with an internal quantum efficiency as high as 90.7% when excited by 460 nm blue light. Moreover, the emission intensity at 423 K retains 84.5% of that at room temperature. The highly efficient and thermally robust luminescence of this material is mainly ascribed to the ultrawide bandgap of host, extremely weak electron–photon coupling effect, defect‐free, and highly structural rigidity. The NIR pc‐LED device fabricated by using the optimized Ca 3 Mg 0.97 Hf 0.97 Ge 3 O 12 :0.06Cr 3+ phosphor combined with blue (λ em = 455 nm) LED chip produces an excellent NIR output power of 49.5 mW @ 11.5% under a driving current of 150 mA, which indicates a superiority to the device fabricated by using the well‐known efficient ScBO 3 :Cr 3+ phosphor under the same condition. Therefore, this work not only provides a promising broadband NIR material, but also highlights the design rules for searching high‐performance NIR materials toward spectroscopy applications.