Synthesis and study of luminescence properties of a deep red–emitting phosphor K 2 LiAlF 6 :Mn 4+ for plant cultivation

Light is the most important component in plant growth and development. This study synthesised a novel Mn 4+ ‐doped K 2 LiAlF 6 red‐emitting phosphor using the coprecipitation method. We observed that on addition of dopant Mn 4+ ions to the host K 2 LiAlF 6 , its phase changed from rhombohedral to cubic due to the change in the lattice position of the atoms. When the atoms are excited at 468 nm, the K 2 LiAlF 6 :Mn 4+ phosphor exhibited a red emission band ranging from 630 to 700 nm, centred at 638 nm, which matched well with the absorption spectra of phytochrome PR. The critical quenching content of Mn 4+ ions was ~3 mol%. The critical distance between Mn 4+ ions was determined to be 19.724 Å, and non‐radiative energy transfer among the nearest‐neighbour Mn 4+ ions was the mechanism used for the concentration quenching effect. The Commission International de l'Eclairage (CIE) chromaticity coordinates of the K 2 LiAlF 6 :0.03 Mn 4+ sample were ( x = 0.7162, y = 0.2837). The luminescence mean decay time was calculated to be 8.29 ms. These results demonstrated the promising prospect of K 2 LiAlF 6 :Mn 4+ as a red‐emitting phosphor for application in red light‐emitting diodes for plant cultivation.