Achieving an ultra-high absorption efficiency in a monoclinic LiAlP2O7:Cr3+ near-infrared phosphor

Near-infrared phosphor-converted light-emitting diode (NIR pc-LED) is becoming a smart light source for portable multifunctional devices, utilizing in fields like bio-imaging, night-vision, and food-quality analysis. However, developing broadband, inexpensive, and efficient NIR phosphors are still in great challenges. Herein, we report a phosphate LiAlP 2 O 7 :Cr 3+ phosphor by choosing highly distorted and inexpensive octahedral Al 3+ -containing compound as host. This material generates a broadband NIR emission with peak located at 844 nm and a full width at half maximum (FWHM) of 163 nm under 450 nm excitation. Amazingly, the absorption efficiency (AE) was measured to be as high as 64%, being higher than most of Cr 3+ -activated polycrystalline materials . Unfortunately, the internal quantum efficiency (IQE) was only 26.7%, and the emission intensity at 373 K kept only 56% of that at room temperature . The detailed reasons for these undesired properties are systematically investigated. Moreover, a prototype NIR pc-LED fabricated by using this material combining with 450 nm LED chip demonstrates a NIR output power of 9.7 mW and NIR photoelectronic conversion efficiency of 3.3% under 100 mA driving current, indicating the feasibility of this material to be applied in NIR pc-LEDs.