Color stable Mn-activated oxidofluorides as conversion luminescent materials for LED-based solid state light sources

A compound of the general formula (I):

• A3BF2M1−xTxO2−2xF4+2x (I)
• doped with Mn(IV), wherein:
• A is selected from the group consisting of Li, Na, K, Rb, Cs, Cu, Ag, TI, NH4, NR4 and mixtures of two or more thereof, where R is an alkyl or aryl group;
• B is selected from the group consisting of H and D and mixtures thereof, where D is Deuterium;
• M is selected from the group consisting of Cr, Mo, W, Te, Re and mixtures of two or more thereof;
• T is selected from the group consisting of Si, Ge, Sn, Ti, Pb, Ce, Zr, Hf and mixtures of two or more thereof;
• 0≤x≤1;
• and
• a surface of the compound is coated another compound.

A light emitting device, comprising:

• a substrate;
• a light emitting diode disposed on the substrate;
• and
• a wavelength converter disposed on the substrate, wherein:
• the wavelength converter includes a plurality of phosphors, and white light is formed by mixing light emitted from the light emitting diode and each of the plurality of phosphors;
• and
• at least one of the plurality of phosphors is an Mn(IV)-activated luminescent material based on an oxidohalide host lattice;
• and
• the wavelength converter includes a first wavelength converter and a second wavelength converter stacked one over another.