Broadband near-infrared luminescence in a cubic pyrophosphate Al0.5Ta0.5P2O7:Cr3+ phosphor for multi-functional applications

Abstract

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) are considered as next-generation of NIR light sources for spectroscopy. However, it is still a challenge to develop an inexpensive broadband NIR phosphor with relatively long-wavelength (λ_em > 800 nm) emission. In this work, an octahedral Al³⁺-containing pyrophosphate Al_0.5Ta_0.5P₂O₇ with a cubic structure was chosen as a host for Cr³⁺. Synthesizing this material indicates that this phosphor exhibits a broadband NIR emission peaking at 850 nm with a full width at half maximum (FWHM) of 155 nm under 465 nm excitation. The crystal structure, morphology, local structure, and photoluminescence properties of this material were investigated in detail. The results revealed a full understanding of this new material. A NIR pc-LED device fabricated by using this material combined with a 450 nm LED chip generates a NIR output power of 10.7 mW and a NIR photoelectric conversion efficiency of 3.4% under a 100 mA driving current, which shows the possibility of this material to be utilized in NIR pc-LED applications. Moreover, this material exhibits a linear relationship between emission intensity, decay time and temperature in a wide temperature range, implying that excellent multi-model temperature sensing applications can be expected.