Enhancing solar energy utilization: A red-emitting Sr2In0.5Sb0.5O4:Mn4+ phosphor with both UV and green excitation for plant growth

Red light in sunlight promotes plant growth and development, while UV and green light are poorly absorbed by plants. Converting UV and green light into red light can enhance solar energy utilization and improve photosynthetic efficiency, significantly shortening the plant growth cycle. Herein, we report a novel red-emitting Sr2In0.5Sb0.5O4:Mn4+ phosphor that can be effectively excited by both UV and green light. According to Dexter's theory, Mn4+ is calculated to be in a weak crystal field. When excited at 330 or 520 nm, the characteristic photoluminescence (PL) peak appears at ∼695 nm, which is attributed 4T2g → 4A2g transition of Mn4+. The optimal doping concentration of Mn4+ is 0.003, and the concentration quenching mechanism was determined to be a dipole-dipole interaction. Additionally, a red LED device was fabricated by encapsulating Sr2In0.5Sb0.497O4:0.003Mn4+ phosphor with a 365 nm UV chip, exhibiting bright red light when driven by 150 mA current. The corresponding electroluminescence (EL) spectrum matches well with the absorption spectra of phytochromes PR and PFR, indicating that Sr2In0.5Sb0.5O4:Mn4+ phosphor has promising applications in plant growth.