Mn4+激活氟化物发光材料的软化学合成、性能优化及其在白光LED器件中的应用

Compared with traditional incandescent lamp and fluorescent lamp, white light-emitting diodes (WLEDs) have greatly promising application in the field of lighting and display due to their advantages such as high efficiency, energy conservation, and environmental protection. As the luminescence materials have a great influence on the device performance of WLEDs, such as the luminous efficiency, color rendering index, and thermal stability, the luminescent performance of phosphors plays a key role on the development of WLEDs. Nowadays, YAG:Ce3+ yellow phosphor is still the most popular material for fabricating white LEDs. However, because of the lack of red light component in the emission of YAG:Ce3+, it is notoriously difficult to make warm white LEDs with high color-rendering index (CRI) and low correlated color temperature(CCT), both of which are key requirements for some important applications such as indoor lighting, and the difficulty can be overcome by adding a suitable red phosphor to complement the red light component to LEDs. When situated at fluoride hosts with octahedral coordination, Mn4+ ions exhibit the most intense broadband excitation at about 460nm and very sharp emission lines peaking at around 630nm. These unique optical characteristics meet the spectral requirements for an ideal red phosphor and thus enable the family of Mn4+-doped fluoride compounds as promising candidates of red emitting phosphors for blue-chip excited warm white LEDs. In this project, a series of Mn4+ doped fluoride compounds such as A2MF6、AMNF6 and AREF4 will be synthesized and studied with the method of cation exchange reaction route. Influence of the ion substitution and crystal structure variation, especially the variation of microstructure on the photoluminescence properties of Mn4+ will be investigated in depth, and the luminescent mechanisms related with crystal structure will be proposed in this project. The research work for the corresponding application in WLEDs device would be carried out.

由于具有节能、环保、小型固化以及长寿命的特点，白光LEDs被认为是下一代主要照明光源。荧光粉性能的优劣对白光LED 技术的发展起着关键作用。目前所采用YAG:Ce3+荧光粉由于红光组分不足，导致器件色温大、显色指数低，限制了器件室内照明应用。Mn4+掺杂于具有八面体配位构型的氟化物可作为白光LED的红光材料。本项目采用离子交换软化学法分别合成Mn4+掺杂的A2MF6、AMNF6以及AREF4构型的氟化物，研究基质材料结构、合成方法以及掺杂浓度对材料光学特性的影响；研究离子取代、结构改变对Mn4+离子发光性质的影响，进行材料发光特性/结构的计算与拟合，揭示Mn4+离子发光本质及其影响因素；获得形貌、颗粒尺寸分布均匀的纯相系列Mn4+激活红色发光材料，并将其应用到LED器件中，考察不同荧光粉用量对器件光学特性的影响。

为了有效基于蓝色芯片白光LED器件WLED中的红光发射不足而导致的色温较高的问题，可被蓝光激发的红色荧光粉是必不可少的组分。目前，对Mn4+掺杂氧化物红色荧光粉的研究是解决PC-WLEDs中红色组分不足的一个热门课题。本项目分别合成了不同基质中Mn4+的光学特性，通过X射线衍射研究样品结构，通过荧光光谱等研究样品的光学特性，研究了样品发光强度与晶体结构的关系，提出并验证了共振荧光增强（REE）的机理。选取其中的最佳发光性能的样品，通过调节与黄色荧光粉的不同配比进行封装，研究了器件的各种光学特性。所合成样品具有较高的流明效率（105 lm/W）和显色指数(Ra = 90.5)以及较低的色温(CCT = 3385 K)，证明材料具有潜在的应用价值。