Ion exchange-assisted surface passivation toward highly stable red-emitting fluoride phosphors for light-emitting diodes.

A facile and environmentally friendly ion exchange-assisted surface passivation (IASP) strategy is presented for synthesizing red emitting Mn-activated fluoride phosphors. A substantial, pristine Mn-free shell layer, applied as a coating to Mn doped potassium fluorosilicate KSiF:Mn (KSFM) phosphors, enhances both water resistance and luminescence efficiency. The stability test of fluoride in water at ambient temperature and boiling water demonstrates that IASP-treated KSFM phosphors are highly water resistant.