The role of co-dopants on the luminescent properties of α-Al2O3:Mn4+ and BaMgAl10O17:Mn4+

Mn4+ doped aluminate materials with efficient red emission are promising components for warmer white light-emitting diodes. However, it still remains as a challenge on increasing its luminous efficiency. For Mn4+ doped aluminate phosphors, co-dopants such as Li+, Mg2+, Na+, Si4+, or Ge4+ ions are often added to tailor the photoluminescence properties of phosphors during preparing process. However, the role of the ions is still in debate. In this work we took BaMgAl10O17:Mn (BMA:Mn) and alpha-Al2O3:Mn as examples to study the effects of Li+, Mg2+, Na+, and Si4+ on their luminescent properties. The energy levels induced by the co-dopants and some possible intrinsic defects of hosts (Al2O3) were calculated using the first-principles method. It is found that the Mg2+ and Na+ ions, compared with Li+ and Si4+, can prefer to form hole-type defects which enhance the valence stability of Mn4+ and thus enhance the emission intensity of the as-prepared phosphors.