Luminescence Enhancement of K<sub>2</sub>LiAlF<sub>6</sub>:Mn<sup>4+</sup> Phosphors by Zn<sup>2+</sup>-Mediated Charge Compensation for Fast-Response Backlighting Applications
Jiawei Qiang, Henghuan Ruan, Lin Wang, Tianman Wang, Jun Lei, Sen Liao, Shixiong Li
Abstract
Wide-spectrum displays require narrow-band red phosphors activated by Mn 4+, but most of them, such as K 2 SiF 6:Mn 4+, have long fluorescence decay lifetimes (>7 ms) that hinder their use in fast-response backlights. Interestingly, K 2 LiAlF 6:0.05Mn 4+ has a shorter fluorescence lifetime (3.43 ms), but its disadvantage is that its luminescence intensity is relatively weak. So, in this study, the luminescence intensity of K 2 LiAlF 6:0.05Mn 4+ is improved by doping with Zn 2+ . The experimental results show that enhancement of the luminous intensity is as high as 39%, the fluorescence lifetime is only increased by 13% (3.89 ms), and it is still less than 4 ms. Through experiments and differential charge density calculations, it has been revealed that the luminescence intensity improvement is due to an increased crystalline quality during the synthesis process. Specifically, the co-doping of Zn 2+ reduces the formation of impurity ions Mn 2+ and Mn 3+ and the generation of K + vacancies caused by nonequivalent doping. We demonstrate the advantage of this phosphor over K 2 SiF 6:Mn 4+ in terms of response speed by using a camera. It emits only weak red light after the blue chip stops working for 5 ms, indicating its potential application in next-generation fast-response displays.