Novel SrLaAlO₄:Mn⁴⁺deep-red emitting phosphors with excellent responsiveness to phytochrome P_FRfor plant cultivation LEDs: synthesis, photoluminescence properties, and thermal stability

Abstract

Herein, novel rare-earth-free Mn 4+ -doped SrLaAlO 4 deep-red emitting phosphors were successfully synthesized via a traditional solid-state reaction method. The crystal structure and phase purity of the asprepared samples were confirmed by XRD Rietveld refinement. Photoluminescence properties of SrLaAlO 4 :Mn 4+ phosphors were examined in detail using photoluminescence spectra, decay lifetimes, temperature-dependent emission spectra and internal quantum efficiency measurements. The excitation spectrum obtained by monitoring at 730 nm contained two excitation bands centered at 364 and 520 nm within the range of 200-550 nm due to the Mn 4+ -O 2À charge-transfer band and the 4 A 2g / 4 T 1g , 4 T 2g transitions of the Mn 4+ ions. Under the 364 nm excitation, the SrLaAlO 4 :Mn 4+ phosphors exhibited an intense deep-red emission band in 610-790 nm wavelength range peaking at 730 nm,which was assigned to the 2 E g / 4 A 2g transition of Mn 4+ ions. The deep red emission showed excellent responsiveness to phytochrome P FR , revealing that the SrLaAlO 4 :0.4% Mn 4+ phosphors possessed a possible application in deep-red light-emitting diodes (LEDs) for plant cultivation. The optimal doping concentration of Mn 4+ ions was found to be 0.4 mol%. The critical distance R c for energy transfer among Mn 4+ ions was determined to be 5.86Å and the concentration quenching mechanism was confirmed to be the electric dipole-dipole interaction. In addition, the Commission International de I'Eclairage (CIE) colour coordinates of the SrLaAlO 4 :0.4% Mn 4+ phosphors (0.734, 0.266) were located in the deep red region and the corresponding internal quantum efficiency was measured to be about 29%.The above results confirmed that the as-prepared SrLaAlO 4 :0.4% Mn 4+ deep red emitting phosphors might be a potential candidate for plant cultivation LEDs.

Enhanced photoluminescence and energy transfer performance of Y3Al4GaO12:Mn4+,Dy3+ phosphors for plant growth LED lights

“…As an alternative, Mn 4+doped oxides [14][15][16][17] catch the public's attention due to its attractive luminescence properties of high-efficacy, low cost, high stability and eco-friendliness. Many strategies have been tried out to enhance the photoluminescence emission of Mn 4+ -doped phosphors, such as matrix solid solution modication, [18][19][20] codoped charge compensator 21,22 or uxing agent, 23,24 and energy transfer from sensitizer to activator. [25][26][27] Solid solution treatment is a common method in phosphor modication with many advantages such as increase lattice distortion and lattice rigidity.…”

Engineering cation vacancies to improve the luminescence properties of Ca14Al10Zn6O35: Mn4+ phosphors for LED plant lamp

“…Presently, the Eu 2+ ‐doped phosphors with red emission are widely studied by many researchers due to the excellent optical properties, including high luminescence efficiencies and thermal stability. Nevertheless, the Eu 2+ ‐doped phosphors are further hindered for indoor plant growth because rare‐earth materials are expensive and the far‐red region in the spectra is insufficient . Alternatively, Mn 4+ with 3d 3 electronic configurations can be excited effectively by blue light and exhibit far‐red emitting due to the spin‐forbidden 2 E → 4 A 2 transition .…”

Mn4+-activated BaLaMgSbO6 double-perovskite phosphor: a novel high-efficiency far-red-emitting luminescent material for indoor plant growth lighting

“…[15][16][17][18][19] Generally, Mn 4+ ions can substitute for W 6+ , Sn 4+ , Sb 5+ , Al 3+ , Ge 4+ , Ta 5+ , and Ti 4+ ions in the octahedral or distorted octahedral systems. [20][21][22][23][24][25][26][27][28][29][30] Just recently, Mn 4+ doped oxide-based phosphors with excellent luminescent properties and chemical stability such as Li 2 MgZrO 4 :Mn 4+ , Ca 3 La 2 W 2 O 12 :Mn 4+ , and La(MgTi) 1/2 O 3 :Mn 4+ have been researched for their potential applications in far-red LEDs for indoor plant growth. [31][32][33] It is known that far-red light around 730 nm (700-740 nm) is most needed for photosynthesis in all plant growth, especially the growth of plant stems.…”