Enhanced deep-red emission from Mn ⁴⁺ /Mg ²⁺ co-doped CaGdAlO ₄ phosphors for plant cultivation

Mn ⁴⁺ -Doped oxide phosphors are under intensive investigation owing to their low manufacture cost and attractive luminescent features for indoor plant cultivation applications. However, it is still a challenge to develop Mn ⁴⁺ -doped oxides with high luminescence efficiency and thermal stability. Herein, Mn ⁴⁺ -Mg ²⁺ pairs are incorporated into a CaGdAlO ₄ host to reduce non-radiative channels formed by Mn ⁴⁺ -Mn ⁴⁺ -O ²⁻ clusters. The photoluminescence and quantum efficiency are significantly enhanced after the introduction of Mg ²⁺ ions to the host. A prolonged Mn ⁴⁺ decay time is also obtained from the Mn ⁴⁺ /Mg ²⁺ co-doped samples. Intense red emission with a narrow peak at 712 nm due to the ² E _g → ⁴ A _2g transition of Mn ⁴⁺ ions is observed under 335 nm excitation. LEDs fabricated by coating the synthesized phosphor on a 365 nm near-UV chip exhibit an intense deep-red emission with CIE chromaticity coordinates of (0.712, 0.285). The results indicate Mn ⁴⁺ /Mg ²⁺ co-doped CaGdAlO ₄ phosphors may be applicable to plant cultivation fields.