【作者】 杨静；

【导师】 周文理；

【作者基本信息】 湖南师范大学 ， 化学， 2021， 硕士

【摘要】 白光发光二极管（WLEDs）由于具有高发光效率、绿色环保、制备简单等优点被广泛应用在照明和液晶显示等领域。市场上流行的WLEDs的封装方式主要是蓝色In Ga N芯片与Y₃Al₅O₁₂:Ce3+（YAG:Ce3+）黄色荧光粉相结合。但是,在器件WLEDs中只添加黄色荧光粉会导致一些问题,比如光源色温偏高（CCT>4000 K）、显色指数偏低（CRI,Ra<80）。寻找合适的红色荧光粉是改善器件WLEDs的光色性能的关键。最近,Mn⁴⁺掺杂的氟化物荧光粉在固态照明领域引起了极大的关注,成为WLEDs中最有潜力的红色荧光粉之一。Mn⁴⁺掺杂的氟化物红色荧光粉具有多项优点,比如红光发射带窄、量子产率高、热稳定性能优异等。然而,Mn⁴⁺掺杂的氟化物红色荧光粉存在耐湿性差的问题。在潮湿的环境中,Mn⁴⁺容易水解为锰的氧化物和氢氧化物,导致荧光粉的发光效率下降,严重影响WLEDs的实际应用。因此,本论文选择的研究方向是Mn⁴⁺掺杂氟化物红色荧光粉耐湿性的改善策略与机制。本文的主要研究内容及成果如下:（1）提出了乙醛酸（GA）钝化表面的策略。基于GA溶液的还原性,有效地去除氟化物表面的Mn⁴⁺,在K₂Si F₆:Mn⁴⁺红色荧光粉表面形成一层同质的K₂Si F₆保护壳层。经过乙醛酸钝化后的荧光粉K₂Si F₆:Mn⁴⁺-GA展现了较高的发光效率和良好的抗湿性能。荧光粉K₂Si F₆:Mn⁴⁺-GA的发光强度约为KSFM发光强度的99.7%。经过360h的水浸,K₂Si F₆:Mn⁴⁺-GA荧光粉仍能维持起始荧光强度的97.5%,内量子产率高达98.43%。用乙醛酸溶液改善荧光粉的耐湿性这一策略同样适用于K₂Ge F₆:Mn⁴⁺和K₂Ti F₆:Mn⁴⁺荧光粉。已水解的氟化物荧光粉也可以经乙醛酸溶液修复,体色恢复到原来的黄色,发光强度可恢复到未水解K₂Si F₆:Mn⁴⁺的99.1%。以钝化后的氟化物荧光粉作为红光成分,封装的WLED的相关色温（CCT）为3249 K时,流明效率高达126.95 lm/W、显色指数（Ra）高于90。老化（温度85o C,湿度85%）500 h之后,WLEDs仍能维持起始流明效率的85%。（2）采用-羟基酸乳糖酸（LA）钝化的策略以改善K₂Si F₆:Mn⁴⁺荧光粉的耐湿性。经LA钝化的氟化物(K₂Si F₆:Mn⁴⁺-LA)的发光强度维持了KSFM的99.4%。水浸360 h之后,K₂Si F₆:Mn⁴⁺的发光强度降至63%,而K₂Si F₆:Mn⁴⁺-LA荧光粉仍能维持起始发光强度的87.5%。乳糖酸溶液同样可以提高荧光粉K₂Ge F₆:Mn⁴⁺和K₂Ti F₆:Mn⁴⁺的耐湿性。此外,乳糖酸溶液也可以修复已水解的氟化物荧光粉,恢复其发光性质。以表面钝化的氟化物为红光成分封装得到的WLEDs具有高流明效率（130.61 lm/W）、低色温（3518 K）和高显色指数（88.5）。在高温和高湿（温度85o C,湿度85%）的环境下老化500 h后,该WLEDs依然能够维持初始流明效率的90.5%。本工作中,用乙醛酸和乳糖酸溶液处理氟化物荧光粉的实验步骤简单,并且成本低廉,为大批量合成耐湿性好的氟化物荧光粉提供了参考。更多还原

【Abstract】 White light-emitting diodes（WLEDs）are widely used in indoor lighting and liquid crystal displays due to their high luminous efficiency,green environmental protection,and simple preparation.The popular WLEDs packaging method on the market is mainly a combination of blue In Ga N chips and YAG:Ce³⁺(Y₃Al₅O₁₂:Ce³⁺)yellow phosphors.However,adding only yellow phosphors to WLEDs will cause some problems,such as high light source color temperature（CCT>4000 K）,low color rendering index（CRI,Ra<80）.Finding suitable red phosphors is the key to improving the light and color performance of WLEDs.Recently,Mn⁴⁺-doped fluoride phosphors have attracted great attention in the field of solid-state lighting and have been rated as the most promising red phosphors in WLEDs.Mn⁴⁺doped fluoride red phosphor has many advantages,such as narrow red light emission,high quantum yield,excellent thermal stability and low production cost.However,the Mn⁴⁺-doped fluoride red phosphor has the problem of poor moisture resistance.In humid environment,Mn⁴⁺is easily hydrolyzed into manganese oxides and hydroxides,resulting in a decrease in the luminous efficiency of the phosphor,which has a certain impact on the practical application in the field of WLEDs.Therefore,the research direction chosen in this paper is the strategy and mechanism of improving the moisture resistance of Mn⁴⁺doped fluoride red phosphor.The main research content and results of this article are as follows:（1）A strategy to passivate the surface with glyoxylic acid（GA）is proposed.Based on the reducibility of GA solution,it effectively removes Mn⁴⁺on the surface of fluoride,forming a homogeneous K₂Si F₆ protective shell layer on the surface of K₂Si F₆:Mn⁴⁺red phosphor.The phosphor K₂Si F₆:Mn⁴⁺-GA passivated by glyoxylic acid exhibits high luminous efficiency and good moisture resistance.The luminous intensity of phosphor K₂Si F₆:Mn⁴⁺-GA is about 99.7%of KSFM luminous intensity.After 360 hours of water immersion,K₂Si F₆:Mn⁴⁺-GA phosphor can still maintain 97.5%of the initial fluorescence intensity,and the internal quantum yield is as high as 98.43%.The strategy of using glyoxylic acid solution to improve the humidity resistance of phosphors is also applicable to K₂Ge F₆:Mn⁴⁺and K₂Ti F₆:Mn⁴⁺phosphors.The hydrolyzed fluoride phosphor can also be repaired by glyoxylic acid solution,the body color is restored to the original yellow,and the luminous intensity can be restored to 99.1%of the unhydrolyzed K₂Si F₆:Mn⁴⁺.With passivated fluoride phosphor as the red light component,when the correlated color temperature（CCT）of the packaged WLED is 3249 K,the lumen efficiency is as high as 126.95 lm/W and the color rendering index（Ra）is higher than90.After 500 hours of aging（temperature 85o C,humidity 85%）,WLEDs can still maintain 85%of the initial lumen efficiency.（2）The-hydroxy acid lactobionic（LA）passivation strategy is used to improve the moisture resistance of K₂Si F₆:Mn⁴⁺phosphors.The luminescence intensity of LA passivated fluoride(K₂Si F₆:Mn⁴⁺-LA)maintains 99.4%of KSFM.After 360 hours of water immersion,the luminous intensity of K₂Si F₆:Mn⁴⁺dropped to 63%,while the K₂Si F₆:Mn⁴⁺-LA phosphor could still maintain 87.5%of the initial luminous intensity.Lactobionic acid solution can also improve the humidity resistance of phosphors K₂Ge F₆:Mn⁴⁺and K₂Ti F₆:Mn⁴⁺.In addition,the lactobionic acid solution can also repair the hydrolyzed fluoride phosphor and restore its luminous properties.WLEDs packaged with surface passivated fluoride as the red light component have high lumen efficiency（130.61 lm/W）,low color temperature（3518 K）and high color rendering index（88.5）.After 500 hours of aging under high temperature and high humidity（temperature 85o C,humidity 85%）,the WLEDs can still maintain 90.5%of the initial lumen efficiency.In this work,the experimental procedure of treating fluoride phosphors with glyoxylic acid and lactobionic acid solutions is simple and low in cost,which provides a reference for the mass synthesis of fluoride phosphors with good moisture resistance.更多还原