Luminescence Enhancement of K2LiAlF6:Mn4+ Phosphors by Zn2+-Mediated Charge Compensation for Fast-Response Backlighting Applications

Bydoping charge Zn2+, the generation of Mn2+/Mn3+ ions and K+ vacancy as fluorescencequenchers in non-equuivalent doped fluoride phosphor is suppressed,and the fluorescence intensity of K2LiAlF6:Mn4+ is significantly increased by 39%. Wide-spectrum displays require narrow-band red phosphorsactivatedby Mn4+, but most of them, such as K2SiF6:Mn4+, have long fluorescence decay lifetimes (>7ms) that hinder their use in fast-response backlights. Interestingly,K2LiAlF6:0.05Mn(4+) has a shorter fluorescencelifetime (3.43 ms), but its disadvantage is that its luminescenceintensity is relatively weak. So, in this study, the luminescenceintensity of K2LiAlF6:0.05Mn(4+) isimproved by doping with Zn2+. The experimental resultsshow that enhancement of the luminous intensity is as high as 39%,the fluorescence lifetime is only increased by 13% (3.89 ms), andit is still less than 4 ms. Through experiments and differential chargedensity calculations, it has been revealed that the luminescence intensityimprovement is due to an increased crystalline quality during thesynthesis process. Specifically, the co-doping of Zn2+ reducesthe formation of impurity ions Mn2+ and Mn3+ and the generation of K+ vacancies caused by nonequivalentdoping. We demonstrate the advantage of this phosphor over K2SiF6:Mn4+ in terms of response speed by usinga camera. It emits only weak red light after the blue chip stops workingfor 5 ms, indicating its potential application in next-generationfast-response displays.