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

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 Ca3MgHfGe3O12:Cr3+ NIR phosphor is discovered, which exhibits a broadband NIR emission (lambda(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 Ca3Mg0.97Hf0.97Ge3O12:0.06Cr(3+) phosphor combined with blue (lambda(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 ScBO3:Cr3+ 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.