Photoluminescence properties of a ScBO:Cr 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 ScBO:Cr 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 ScBO:Cr, as well as its applications for NIR pc-LEDs, were systematically investigated. ScBO:Cr 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, Cr ions occupy the Sc sites with relatively low crystal field strength in the ScBO host, and therefore ScBO:Cr phosphors show intense broadband emission peaking at ∼800 nm upon excitation at 460 nm, originating from spin-allowed T → A transition of Cr ions. The optimum Cr 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 ScBO:Cr 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 ScBO:Cr phosphors for applications in broadband NIR pc-LEDs.