Novel far-red-emitting SrGdAlO4:Mn4+ phosphors with excellent responsiveness to phytochrome PFR for plant growth lighting

Abstract

In this work, we reported on novel far-red-emitting SrGdAlO₄:Mn⁴⁺ (SGA:Mn⁴⁺) phosphors towards application in plant growth lighting. The crystal structure and luminescence properties were investigated on the basis of X-ray diffraction, excitation and emission spectra, luminescence decay curves and temperature-dependent photoluminescence spectra. When excited by 353 nm, the SGA:Mn⁴⁺ phosphors showed a far-red emission band in the 650–800 nm wavelength range with peaks at 709 and 725 nm, which was due to the ²E_g → ⁴A_2g electron transition of Mn⁴⁺ ion. The optimal Mn⁴⁺ doping concentration was about 0.1 mol%. The CIE chromaticity coordinates of the SGA:0.1%Mn⁴⁺ sample were (0.7064, 0.2934). The luminescence decay lifetimes decreased gradually from 1.263 to 0.868 ms with the increasing Mn⁴⁺ concentrations. Notably, the emission band of SGA:0.1%Mn⁴⁺ sample was well-matched with the absorption spectrum of phytochrome P_FR, which indicated the SGA:Mn⁴⁺ were potential far-red-emitting phosphors for plant growth applications.