Thermally stable La2LiSbO6:Mn4+,Mg2+ far-red emitting phosphors with over 90% internal quantum efficiency for plant growth LEDs

Abstract

In this paper, we reported on the high-efficiency and thermally-stable La₂LiSbO₆:Mn⁴⁺,Mg²⁺ (LLS:Mn⁴⁺,Mg²⁺) far-red emitting phosphors. Under 338 nm excitation, the composition-optimized LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors which were made up of [SbO₆], [LiO₆], and [LaO₈] polyhedrons, showed intense far-red emissions peaking at 712 nm (²E_g → ⁴A_2g transition) with internal quantum efficiency as high as 92%. The LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors also exhibited high thermal stability, and the emission intensity at 423 K only reduced by 42% compared with its initial value at 303 K. The far-red light-emitting device has also been made by using the LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors and a 365 nm emitting InGaN chip, which can emit far-red light that is visible to the naked eye. Importantly, the emission spectrum of the LLS:0.3%Mn⁴⁺,1.6%Mg²⁺ phosphors can match well with the absorption spectrum of phytochrome P_FR, indicating the potential of these phosphors to be used in plant growth light-emitting diodes.