Synthesis and photoluminescence properties of deep red-emitting CaGdAlO4:Mn4+ phosphors for plant growth LEDs

In this work, we reported on novel Mn4+-activated CaGdAlO4 (CGA) deep red-emitting phosphors. Under 349 nm excitation, the CGA:Mn4+ phosphors showed a deep-red emission band within the wavelength range of 650-800 nm centered at 715 nm due to the E-2(g) -> (4)A(2g) transition of Mn4+ ions. CGA:Mn4+ phosphors had two broad excitation bands in the 250-550 nm region. The optimal doping concentration of Mn4+ was about 0.2 mol %. The CIE chromaticity coordinates of CGA:0.2%Mn4+ sample were (0.7132, 0.2866), and the lifetimes of CGA:xMn(4+) phosphors monitored at 715 nm showed a decrease with increasing Mn4+ doping concentration in the range of 0.05-1.0 mol%. Importantly, the CGA:0.2%Mn4+ sample had internal quantum efficiency as high as 45%. Finally, a deep-red LED device was prepared by integrating a 365 nm near-UV InGaN chip and CGA:0.2% Mn4+ phosphors.