Chemical trends of Mn4+ emission in solids

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.