Promising near-infrared emitting Cr3+-doped LaMnAl11O19 phosphors for plant growth LEDs with excellent responsiveness to the phytochrome PFR

Abstract

Lately, near-infrared-emitting Cr³⁺-doped phosphors have become the focus of research due to their promising performance in the field of plant lighting. This paper reports a new Cr³⁺-doped LaMnAl₁₁O₁₉ near-infrared (NIR) hexagonal aluminate phosphor, which has high efficiency and good thermal stability, and has potential applications in the plant growth lighting field. LaMnAl₁₁O₁₉ compounds contain abundant [AlO₆] octahedra, which provide a rich coordination environment for Cr³⁺ doping. Upon excitation at 426 nm, the LaMnAl₁₁O₁₉:Cr³⁺ phosphor produces NIR emission with a peak at 706 nm corresponding to the ²E → ⁴A₂ transition of Cr³⁺ ions. In LaMnAl₁₁O₁₉:Cr³⁺ phosphors, the Cr³⁺ ion is in a strong crystal field environment, and the D_q/B value is 3.3. The LaMnAl₁₁O₁₉:4%Cr³⁺ phosphor has an internal quantum efficiency of 55.67% and good thermal stability. The emission spectrum of the LaMnAl₁₁O₁₉:Cr³⁺ phosphor has a significant overlap with that of the photosensitive pigment P_FR, indicating its potential in plant growth lighting applications.