Enhancement in the water resistance and thermal stability of Na3HTiF8:Mn4+ by co-doping with organic amine cations

Mn4+-doped fluoride red light phosphors are widely utilized in various fields, and their luminous performance is influenced by their stability in high humidity and temperature environments. By incorporating TEOAH+ (TEOAH+ = (HOCH2CH2)3NH+) into the Na2TiF6 matrix, Na3HTiF8:Mn4+,TEOAH+ with improved thermal stability and water resistance was synthesized. Enhancement in the luminescence thermal stability is supported by its strong negative thermal quenching (NTQ) effect, which is attributed to the phonon-induced mechanism wherein the probability of radiative transitions increases much faster than the probability of non-radiative transitions. Additionally, the integrated emission intensity of the optimal sample Na3HTiF8:Mn4+,0.15TEOAH+ was maintained at 70.1% after being immersed in water for 360 min, which may be attributed to the addition of TEOAH+ cations in the structure, thus increasing its structural rigidity. The prototype light-emitting diode (LED) has a narrow emission band, 88.6% color gamut, and 83.1 lm W-1 light efficiency, according to the National Television Standards Committee (NTSC). The qualities of the phosphor make it an ideal candidate for back-lighting devices.