Local lattice modulation via Na+ for K+ substitution to enhance luminescence efficiency and thermal stability of Cr3+-doped K3LiMg4(Si2O5)6 NIR phosphors

Cr 3+ -activated phosphor has become the mainstream choice to obtain broadband near-infrared phosphor-converted light-emitting diodes (NIR pc-LED) for the applications of bio-imaging and component nondestructive detection. However, exploring efficient and stable Cr 3+ -activated NIR phosphors is still an important yet formidable challenge. Herein, a series of Na y K 3- y LiMg 4 (Si 2 O 5 ) 6 :Cr 3+ phosphors was synthesized, which exhibits a broadband emission spectrum spanning 650-1100 nm. Utilizing the innovative non-main lattice substitution strategy, the internal quantum efficiency (IQE) of Cr 3+ was enhanced from 21% to 80%, and thermal stability was also improved from 42% to 70%@150 °C. Based on the first-principles theory calculation, the IQE and thermal stability improvement are attributed to the strengthened local structure stability around Cr 3+ caused by the introducing of Na + . Finally, a NIR pc-LED device was packaged by combining the optimized Na 3 LiMg 4 (Si 2 O 5 ) 6 :4%Cr 3+ phosphor with blue LED chip, which demonstrates potential applications in biological imaging and night vision systems.