Optimizing interstitial site luminescence via a sensitizer strategy towards green synthesis of Mn4+-activated fluoride phosphors

Abstract

High water-soluble KHF2:Mn4+ (KHFM) is a potential precursor instead of K2MnF6 for preparation of Mn4+ doped fluoride materials, but it has a lower Mn4+ concentration in precursor causing a poor luminescence performance. Herein, we reported a Ti4+-doped KHFM phosphor with high luminous efficiency, high thermal stability via a sensitizer strategy. Significantly, the luminescence intensity of KHFM:xTi4+ (x = 0.8%) is increased by 4.6 times, besides, the maximum values of the internal quantum efficiency (IQE) and external quantum efficiency (EQE) increased to 81% and 49%, respectively. Further, the weaker zero phonon line (ZPL) at 621 nm (1.997 eV) is accordingly highlighted with the increase of PL intensity after codoping Ti4+ content. These results indicate that introducing suitable ion to interstitial site as sensitizer can promote the introduction of Mn4+ in ion exchange process. Notably, the obtained KHFM:Ti4+, as a particular green precursor material instead of K2MnF6, develops a novel green synthetic route for preparing Mn4+-activated K2SiF6 fluoride phosphors, and is helpful in developing high-performance warm WLED.