Chemical trends of Mn4+ emission in solids

Abstract

Mn⁴⁺ is known to activate red emission in many materials. However, the existing Mn⁴⁺ activated red phosphors have relatively long emission wavelengths and are therefore inefficient for general lighting purposes. Density functional calculations are performed on a large number of Mn⁴⁺ doped materials with diverse crystal structures to understand how material properties of different hosts affect the emission energy of the Mn⁴⁺ dopant. The results show that weak Mn⁴⁺–ligand hybridization generally leads to higher Mn⁴⁺ emission energies. Host materials allowing long Mn–ligand distance and/or significant distortion of bond angles around the Mn octahedral site are shown to have higher emission energies. Several new oxide host materials are found for Mn⁴⁺. Their emission energies are found to be higher than those currently known for Mn⁴⁺ doped oxides and should be closer to that of Y₂O₃:Eu³⁺, which is the current commercial red phosphor for fluorescent lighting.