Narrower band red and green emission in phosphor-converted white lightemittingdiodes (wLEDs) can improve the efficacy and color gamut in lightingand display applications. A promising luminescent ion is Mn~(2+) that can haveboth narrowband green (tetrahedral coordination) and red (octahedral coordination)emission. Unlike in earlier lighting applications of Mn~(2+) phosphors,temperature quenching is important in wLEDs. Insight into the thermalquenching behavior of Mn~(2+) luminescence is lacking. Here systematicresearch is reported for a variety of Mn~(2+)-doped phosphors; a huge variationin the luminescence quenching temperature T_(50), ranging from 50 K for Mn~(2+)in ZnTe to 1200 K in MgAl_2O_4, is revealed. The value T_(50) shows a positivecorrelation with the bandgap of the host, but no correlation with the fullwidth half maximum (FWHM) of the emission band, indicating that thermallyactivated photoionization, not thermal crossover, is the operative quenchingmechanism. This is confirmed by thermally stimulated luminescence (TSL)measurements that show a rise in TSL signal following photoexcitation attemperatures around T_(50) providing evidence that quenching is correlated withgeneration of free charge carriers. Based on these findings, as a design ruleis obtained that for temperature-stable Mn~(2+) luminescence in (high power)LEDs a wide-bandgap host material is required.
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