K2LiScF6:Cr3+/Mn4+ fluoride phosphor with enhanced broadband emission for NIR pc-LEDs

Abstract

Trivalent chromium ion-activated broadband near-infrared (NIR) luminescence materials have shown great application prospects as next-generation NIR light sources, but improvement of the luminescence efficiency remains a challenge. Herein, novel K₂LiScF₆:Cr³⁺ and K₂LiScF₆:Cr³⁺/Mn⁴⁺ broadband fluoride NIR phosphors are designed and prepared by a combination of hydrothermal and cation exchange methods for the first time. The crystal structure and photoluminescence (PL) properties of K₂LiScF₆:Cr³⁺ are studied in detail, which shows strong absorption in the blue light region (λ_ex = 432 nm) and broadband NIR emission (λ_em = 770 nm) with a PL quantum efficiency of 77.6%. More importantly, the NIR emission of Cr³⁺ can be enhanced by co-doping with Mn⁴⁺, which may provide an alternative way for improving the PL intensity of Cr³⁺-activated broadband NIR phosphors. Finally, a NIR phosphor-converted LED (pc-LED) device is fabricated using the as-prepared NIR phosphor and its application in bio-imaging and night vision has been evaluated.