Photoluminescence properties of a ScBO3:Cr3+ phosphor and its applications for broadband near-infrared LEDs

The rapid extension of solid state lighting technologies offers the possibility to develop broadband near-infrared (NIR) phosphor-converted LEDs (pc-LEDs) as novel NIR light sources. In this paper, a new NIR-emitting phosphor ScBO3:Cr3+ was synthesized by a high temperature solid state reaction method. Phase structure, spectroscopic properties, luminescent lifetime, quantum yield, emitter concentration influences and thermal quenching behavior of ScBO3:Cr3+, as well as its applications for NIR pc-LEDs, were systematically investigated. ScBO3:Cr3+ phosphors exhibit a broad absorption band ranging from 400 to 530 nm, which matches well with the characteristic emission of the blue LED chip. Moreover, Cr3+ ions occupy the Sc3+ sites with relatively low crystal field strength in the ScBO3 host, and therefore ScBO3:Cr3+ phosphors show intense broadband emission peaking at ∼800 nm upon excitation at 460 nm, originating from spin-allowed 4T2 → 4A2 transition of Cr3+ ions. The optimum Cr3+ concentration was determined to be ∼2 mol% with a quantum yield of ∼65%. A broadband NIR pc-LED prototype device was fabricated by the combination of ScBO3:Cr3+ phosphors and a blue LED chip, which showed a maximum NIR light output power of ∼26 mW and a corresponding energy conversion efficiency of ∼7%. The results indicate the great potential of ScBO3:Cr3+ phosphors for applications in broadband NIR pc-LEDs.