Design of highly efficient energy transfer phosphor Sr4Al14O25:Eu2+,Mn4+ with deep-red emission and application potential in plant growth

Abstract

Deep-red emitting phosphors at 650–700 nm are highly required for chlorophyll a and chlorophyll b in the photosynthesis process to promote plant growth. Here, single-phased Sr₄Al₁₄O₂₅ (SAO):x%Eu²⁺,y%Mn⁴⁺ (0.02 ≤ x ≤ 0.12, 0.04 ≤ y ≤ 4) phosphors with high energy transfer efficiency were synthesized through a novel two-step high-temperature solid-state method. The divalent valences of Eu ions and tetravalent valences of Mn ions were confirmed using X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy. Under 360 nm excitation, the phosphors exhibit a broad green light emission band and a strong sharp deep-red emission ranging from 630 nm to 700 nm. The decay lifetimes of Eu²⁺ monitored at 492 nm decline from 5.26 μs to 0.98 μs with adjusting the concentration of Mn⁴⁺. Energy transfer from Eu²⁺ to Mn⁴⁺ in the host was demonstrated to be a dipole–dipole interaction with up to 81.3% efficiency. Both the fabricated sunlight-converting films and a light-emitting diode prepared using the Sr₄Al₁₄O₂₅:Eu²⁺,Mn⁴⁺ phosphor indicated that they have high potential for promoting plant growth.