Enhanced deep-red emission from Mn4+/Mg2+ co-doped CaGdAlO4 phosphors for plant cultivation

Abstract

Mn⁴⁺-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 Mn⁴⁺-doped oxides with high luminescence efficiency and thermal stability. Herein, Mn⁴⁺–Mg²⁺ pairs are incorporated into a CaGdAlO₄ host to reduce non-radiative channels formed by Mn⁴⁺–Mn⁴⁺–O²⁻ clusters. The photoluminescence and quantum efficiency are significantly enhanced after the introduction of Mg²⁺ ions to the host. A prolonged Mn⁴⁺ decay time is also obtained from the Mn⁴⁺/Mg²⁺ co-doped samples. Intense red emission with a narrow peak at 712 nm due to the ²E_g → ⁴A_2g transition of Mn⁴⁺ 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 Mn⁴⁺/Mg²⁺ co-doped CaGdAlO₄ phosphors may be applicable to plant cultivation fields.