白光LED用单一基质锡酸盐荧光材料低维晶体结构调控荧光增强机制的研究

The properties of phosphor-converted white lighting emitting diodes (LED) rely critically on the phosphors performance. Although white light is easily achieved in blue LED chip activated yellow phosphor (YAG:Ce) based system, the individual degradation rate between the blue LED and yellow phosphor and the deficiency of red emission cause chromatic aberration and poor white light performance. In order to improve the white light quality and obtain a higher Color Rendering Index (CRI), a ultraviolet (UV) LED chip coated with three emitting blue,green, and red phosphors is introduced. This approach provides white LED with excellent CRI, but a drawback arises of which white light efficiency decreases owning to the strong reabsorption of the blue light by the red and green phosphors. Developing a single-phased white-emitting phosphor using the principle of energy transfer from a sensitizer to an activator in a single host lattice for UV LED is an excellent option to replace the above mentioned appaoches. However, the efficiency of the white light is relative low if the energy transfer process between the donar ions and accept ions doesn't effect. In this work, we aim at to realize the white light emitting in the activators doped single host of stannate, for which possess the self-activated blue emission and could be combined with red and green emission in pursuing the white light. In addition, due to the low-dimensional crystal structure, the self-activated blue emission of stannate could be promoted or surpressed by the differential SnO6 chaining structure, and for the fact that the excitation and emission properties of activators depend strongly on the crystal structure of the host lattice, it is facile to realize the photoluminescent improvement of the white emitting in low-dimensional stannate single-phased phosphor. Therefore, this approach could be available to realize white light emitting in stannate with higher luminous efficacy, excllent CRI and small color aberration. Emphasis will be placed on the relationships among crystal structure, energy transfer process and photoluminescence performance in this work. A comprehensive understanding between the host and the activators will be proposed, of which is of fundamental importance for advancing technological applications, especiallly for white light emitting diodes.

近紫外LED芯片激发单一基质荧光材料实现白光的方式不仅能够有效改善蓝光芯片与黄光组合得到白光的色纯度、显色指数，还避免了三基色荧光粉混合中蓝光光谱能量的再吸收导致其白光效率的下降及色彩还原性的变化等问题，但单一基质中通过敏化剂与激活剂离子之间能量传递实现白光的方式很难保证其具有较高的发光效率。由于锡酸盐所具有的SnO6八面体通过不同的链接方式形成的低维晶体结构表现出自激发射的特点，本项目拟通过构建适当的能量传递途径，实现低维晶体结构锡酸盐作为高效荧光材料单一基质的白光发射。通过探索低维结构调控自激发射对激活离子之间能量传递机制的影响规律，及其晶体结构的调整致其对于激发光吸收效率变化的研究，进一步揭示基质材料结构变化对于单一基质荧光材料发光效率的影响机制。本项目的实施不仅有助于认识材料基质的结构与光活性离子发光效率的规律，而且对于白光LED荧光材料的开发及应用具有重要的理论价值和现实意义。

由于锡酸盐所具有的SnO6八面体通过不同的链接方式形成的低维晶体结构表现出自激发射的特点，本项目通过构建适当的能量传递途径，实现低维晶体结构锡酸盐作为高效荧光材料单一基质的白光发射。通过探索低维结构调控自激发射对激活离子之间能量传递机制的影响规律，及其晶体结构的调整致其对于激发光吸收效率变化的研究，进一步揭示基质材料结构变化对于单一基质荧光材料发光效率的影响机制。项目主要从以下几个方面开展：.(1)低维晶体结构锡酸盐基质的制备及其晶体结构对自激发射影响规律的研究。在所制备的锡酸盐类基质材料中，研究了不同的SnO6八面体链接方式所形成的低维晶体环境中基质的光致发光现象，探索了低维晶体结构影响电荷转移跃迁的自激发射的规律。结果表明基质本身蓝光发射为局域的电子-空穴对的自俘获激发特性，并且该自俘获过程与材料的本征氧空位缺陷有着密切的联系。.(2)研究了激活剂离子在锡酸盐不同晶体场环境中的光致发光特性，明确基质晶体结构对激活剂离子光谱性能的影响机制。并且通过利用基质结构的特性，我们也能够有目的的对发光中心离子的价态进行调控进而改变其发光特性。.(3)探索了低维结构调控自激发射与激活离子间能量传递的过程，结果表明稀土离子掺杂的锡酸盐荧光材料中可以观察到其基质的自俘获发光与激活剂离子的特征发光。通过调配其中各个发光中心的能量分布，可实现该单一基质在全可见光范围内的颜色变化，进而得到白光发射，这一结果表明了Bi3+, Dy3+ , Eu3+掺杂的Ca3SnSi2O9可作为有效的紫外激发单一基质白光发射荧光材料。.(4)通过F-离子的引入，可实现基质低维结构的调控，其结构中扭曲的八面体导致其晶体场强度的变化以及大量氧空位缺陷的形成，这一过程可实现其自俘获发光行为的改善，并且有效提高了发光中心的发光效率。因此，该结果也为改进发光中心离子发光行为提供了有效的途径。