白光LED用卤化钙和氧化钙基双掺杂发光材料的能量传递与光谱调控研究

To explore new luminescent material for near-ultraviolet-based white LEDs, the study on energy transfer of Eu-Mn has been carried out in this project. A high brightness material of CaCl2:Eu, Mn with blue and red dual color emission is obtained. Considering to extend the application area of new material to blue light-based white LEDs, a yellow light-emitting material CaO:Ce is prepared. It has richer red ingredient than YAG:Ce, which is favor of the white light with low color temperature. The hygroscopic of the above-mentioned materials is overcome by Nano-SiO2 coating. The coated materials show weaker thermal quenching characteristics than the commercial YAG:Ce. However, it is shown that the blue and red wavelength in CaCl2:Eu, Mn are shorter than the standard value, and the red ingredient in CaO:Ce is not rich enough to obtain the warm white light that most people prefer. Therefore, in order to obtain high-quality white light, the spectral characteristics need to be further manipulated and improved. Next, we intend to select CaBr2 and CaI2 to replace CaCl2 host. Utilizing the rearrangement of the electron cloud effect, the level center of gravity can be lowered in CaBr2 and CaI2 than in CaCl2, making the blue and red emission redshift and approach to the standard value to fabricate high quality white light. Based on the previous results of energy transfer, we also plan to introduce Mn as a red luminescent center into CaO:Ce host in order to further enhance its red ingredient. All of these can provide the physical basis at the design of new materials for high color rendering and warm white LEDs.

为探索近紫外基白光LED用发光新材料，本项目开展了Eu-Mn能量传递的研究，获得了高亮度蓝、红双色发光的CaCl2:Eu,Mn。还将材料应用目标扩展至蓝光基白光LED，制备出黄色发光材料CaO:Ce，其红光成分比YAG:Ce多，有利于获得低色温白光。上述材料经Nano-SiO2包覆，克服了易潮解的问题，并呈现出比商用YAG:Ce弱的热猝灭特性。为获得高品质白光，材料光谱特性还需进一步调控和改进。研究表明，CaCl2:Eu,Mn的蓝、红光波长偏短；CaO:Ce的红光成分还不足以合成人们更喜欢的暖白光。下一步研究拟选择CaBr2和CaI2取代CaCl2基质，利用电子云重排效应使能级重心降低,实现蓝、红光波长红移；基于前期能量传递的研究结果，在CaO:Ce中引入红色发光中心Mn，旨在进一步增强红光成分,为获得高显色性、暖白光LED提供新型发光材料设计的物理基础。

基于白光LED的固态照明光源具有低耗能、长寿命等优点，正逐渐取代传统照明光源走入千家万户。目前，商用白光LED实现白光的方案主要为蓝光LED芯片封装光转换荧光粉，其中光转换荧光粉对合成的白光光谱质量起关键作用。为获得高显色、低色温的高质量白光，需要将绿、黄、红几种荧光粉混合，实现白光光谱成分的均衡分布。但混合后的荧光粉存在辐射再吸收、老化特性不一致等问题，导致白光LED器件流明效率下降和光谱不稳定，因此需要开发具有光谱成分均衡分布的单一基质荧光粉材料。本项目在前期研究工作基础上，提出选择高效黄色发光材料Ce3+掺杂氧化钙为母体，探索基于蓝光LED芯片激发的全光谱单一基质荧光粉，为实现高显色白光LED奠定基础。项目组在CaO:Ce3+中引入红色发光中心Mn2+，利用Ce3+→Mn2+能量传递实现Mn2+高效红色发光，研究了Ce向Mn能量传递的发光动力学过程，能量传递效率最高达94 %，离子间临界距离为10.5 Å。同时，进行了实用性研究，获得了低色温高显色白光LED器件，色温为3973 K，显色指数为83.1 %。结果表明，项目组研制的这种新型单一基质荧光粉材料具有光谱成分分布均衡、合成简单、成本低等优点，作为一种新型适合蓝光LED芯片激发的单一基质荧光粉，有潜力应用于白光LED照明领域。本项目对于设计开发具有我国自主知识产权的先进LED荧光粉，促进我国固态照明研究与产业的发展具有重要意义。