Red shift properties, crystal field theory and nephelauxetic effect on Mn⁴⁺-doped SrMgAl_10-yGa_yO₁₇ red phosphor for plant growth LED light

The discovery of novel Mn⁴⁺-doped oxide red phosphor with suitable spectrum for plant growth is a hot issue in the recent years due to the characteristic red photoluminescence of ²E_g → ⁴A₂ transition in Mn⁴⁺ ions. Generally, the emission position of Mn⁴⁺ is hard to tune because of specific crystal field in most phosphors. In this work, tunable luminescence property with obvious red shift in the spectra is observed in the Mn⁴⁺-doped SrMgAl_10-yGa_yO₁₇ red phosphor via simple substitution of Ga³⁺ for Al³⁺, and crystal field theory and nephelauxetic effect are employed to explain this phenomenon. Meanwhile, the Ga³⁺ dopant changes the shape of the spectra because Ga³⁺ dopant guides the replacement site of Mn⁴⁺ and changes the luminescence center. Improved emission intensity is obtained because appropriate Ga³⁺ doping leads to larger band gap and reduces non-radiative transitions. Phosphor-converted LED (pc-LED) devices fabricated with blue chip (470 nm) and the as-obtained SrMgAl_10-yGa_yO₁₇:1.0%Mn⁴⁺ phosphors emit bright blue and red light, which fit the absorption regions of plant pigments well, thus SrMgAl_10-yGa_yO₁₇:Mn⁴⁺ phosphor can be a candidate for plant growth LED light.