Efficient Ultra‐Broadband Phosphors for High-Power Near-infrared LED and night vision imaging system sources

Broadband near-infrared (NIR)-emitting materials have critical applications in biology, medical detection, and NIR night-vision. However, developing NIR phosphors with promising optical properties and excellent thermal stability is a great challenge for research. In this work, a novel NIR phosphor Cr3+ and Yb3+ doped CaSc2O4 (CSO) is an evolving NIR emitting phosphor with decent optical properties, boosted emission intensity, and thermal stability that makes it a promising candidate with potential applications in NIR-LED and infrared night-vision. The implications of the fundamental electronic structure of CSO, including valence-band (VB) and conduction-band (CB) orbital character, are investigated. Under blue light excitation, CSO:Cr3+ is settled with pure broadband NIR emissions (max = 920 nm, FWHM (full width at half maximum) = ∼310 nm) and good thermal stability. The occupation of two selectable lattice sites of Cr3+ in CSO is discussed in detail. Furthermore, emission enhancements of samples are done by Cr3+ and Yb3+ codoping, effectively broadening FWHM to 351 nm and reducing thermal quenching. The energy transfer (ET) routes in CSO:Cr3+,Yb3+ are investigated based on PL lifetime and comprehensive kinetic ET model, revealing that the PL enhancements by Cr3+ and Yb3+ codoping mainly originate from the ET from Cr3+ to Yb3+ emitters with more efficient and thermally stable. Finally, an InGaN-LED device encapsulated using CSO:0.01Cr3+ and CSO:0.01Cr3+,0.01 Yb3+ phosphor was fabricated. The fabricated NIR pc-LEDs are excellent candidates for NIR light sources in biological imaging and NIR night vision.