近紫外激发Y2MoO6单一相稀土白光材料的制备、发光机理及LED器件研究

To date, phosphor-converted white light-emitting diodes (WLEDs) are emerging as an indispensable solid-state light source for the next generation lighting industry and display systems due to their unique properties including but not limited to energy savings, environment-friendliness, small volume, and long persistence compared with the traditional lighting sources. However, it still faces the challenges in the improvement of luminous efficiency, color rendering index, color stability, which are closely related to the optical properties of phosphors. An overwhelming contribution has been made to the development of phosphors in WLEDs with the advent of science and technology, such as micro- and nano-solid material synthesis, functionalization and characterization of materials, as well as the emergence of novel luminescent materials. Single-phase white-emitting host materials can avoid color reabsorption and ratio control problems among phosphors, and improve the color rendering and luminous efficiency. Therefore, white light generation in a single-phase host is a hot research topic now. With the progress of UV LEDs (350-410 nm), WLEDs fabricated by UV-LEDs chip coated with single-phase white-emitting phosphors show more and more advantages. In this project we propose to explore sol-gel and solvothermal synthesis to gain size and morphology-controllable Y2MoO6-based phosphors with a strong absorption at near UV range. Two modes of codoping (Tb3+/Eu3+ or Tb3+/Sm3+) and tridoping (Ce3+/Tb3+/Eu3+ or Ce3+/Tb3+/Sm3+) will be applied to generate white light under the excitation of near UV light. It is reported that the unique properties of rare-earth ions emission are often strongly dependent on the grain size, composition, surface, dimension and micro structure. Also, the position of charge transfer band of the host is closely related to crystal lattice parameters. Thus, the nature how macro and micro structure affect their luminescence properties is explored in detail. Especially, the energy transfer from the host to activator ions and sensitizer to activator ions in different surroundings will be illustrated by means of excitation spectra, emission spectra and life-time measurements for the optimization design of single-phase WLEDs phosphors. In further, high-quality WLEDs will be assembled combining the single-phase phosphors and commercial near-UV LEDs. We have no reason to doubt that this work will lay the experimental and theoretical basis for the design and synthesis of novel single-phase WLEDs phosphors.

对于将成为新一代照明光源的白光LED，如何提高其发光品质（如高流明效率、显色指数、色彩稳定性等）是目前面临的挑战。而这些与所用荧光粉的发光性能密切相关。随着近紫外LED（350 -410 nm）技术的进步，发展与其相匹配的单一相稀土荧光材料被认为是解决上述难题的有效手段。本项目拟选取在近紫外有强吸收的Y2MoO6为基质，设计双掺激活离子Tb3+/Eu3+（或Sm3+）、三掺敏化离子Ce3+、激活离子Tb3+、Eu3+（或Sm3+）两种模式实现白光。采用溶胶-凝胶及溶剂热方法合成出不同尺寸和形貌的单一相白光材料，分析晶体结构、微结构等影响其发光性能的物理本质，建立相应的“构-效关系”。尤其要通过激发谱、发射谱、荧光寿命等深刻阐述基质和离子、离子和离子之间的能量传递机理，为进一步优化单一相稀土白光材料的设计提供理论依据。在此基础上，将白光材料和近紫外LED相结合，组装出高品质单一相白光LED。

近紫外激发单一相稀土离子白光LED的品质（如发光强度、显色指数、色彩纯度等）与荧光粉的性能密切相关，而荧光粉的发光性质则决定于基质与掺杂离子及掺杂离子之间的相互作用。本项目主要研究了几种白光LED用荧光粉，如稀土掺杂钼酸钇、稀土掺杂钼酸钙、稀土掺杂钨酸钇及稀土掺杂硼酸钇等体系的发光性能。通过溶胶-凝胶及溶剂热等不同方法合成出了分散性好、尺寸可调、形貌和微结构可控的样品，阐明了晶体结构（基质电荷迁移带位置等）和微观结构（如稀土离子占据格位及对称性等）与发光性质之间的构效关系。在此基础上，以发光学能量转移理论为指导，通过激发谱、发射谱、荧光寿命等深刻阐述了基质和离子之间、离子和离子之间的能量传递机理，为进一步优化单一相白光材料的设计提供了理论依据。最后，将白光材料和商用近紫外LED相结合，组装出高性能白光LED，实现了从设计到制备再到应用的完整流程。可以相信，本课题的实施将对单一相白光LED的应用产生积极的推动作用。同时，设计和搭建了高压条件下的荧光光谱测试系统、高低温荧光及寿命测试系统、高分辨格位选择光谱测试系统等先进平台，为发光学领域的研究提供了重要的技术支撑。