硅酸盐长余辉发光材料长余辉机理的第一性原理研究

With the further advance of silicate phosphors applications, the relevant research need provide accurate and profound theoretical guidance for the preparation of the efficient long afterglow materials in micro-scale, but not just confined to applications. Typically, the theoretical basis for the preparation process of high-quality long afterglow silicate materials, the codoping of different types of activator, and the selecting of different basis matrix composition requires expansion from the existing semi-empirical and controversial mechanism models into fully resolved trap microscopic states. This project intends to focus on the problem about long afterglow mechanism, such as the identity of the carriers, the trap sources, and the trap depth control. Starting from the trap sources assumption which existed model, selecting intrinsic defects, rare earth ion impurities, as well as a composite of them as the research object, we study the morphology and level structures of the luminescent center ions and the various traps based on defects perspectives and investigate the luminous origin and performance regulation of silicate phosphor by a combination of first-principles theoretical judgment and experimental approach. This project provides a reference for the development and performance optimization of silicate long afterglow materials, and promotes the applications of the first-principles study in long afterglow luminescent materials research fields. This basic research work is significant on both the exploration of the novel long afterglow luminescent materials and academic research.

随着硅酸盐长余辉发光材料实用化进程的推进，其研究已难以停留在应用开发层面，需要深入到微观尺度为高效长余辉材料的制备提供准确而深刻的理论指导，典型地表现在获得高品质硅酸盐长余辉材料的优化制备工艺、共掺杂不同种类的激活剂和选择不同的基质组成等有效途径所需的理论基础要求从现有半经验、尚有争议的机理模型推向完全解析的陷阱微观状态。本课题拟围绕载流子身份、陷阱来源、陷阱深度调控等长余辉机理问题，从现有模型中陷阱来源的假设出发，分别选择本征缺陷、稀土离子杂质、以及二者组成的复合杂质等陷阱体系作为研究对象，通过第一性原理计算的理论判断与实验相结合的方法，从缺陷角度研究发光离子和各种陷阱的形态和能级结构，探讨硅酸盐长余辉发光的起源及性能调控，为硅酸盐长余辉材料的研发和性能优化提供一定的参考依据，同时推进第一性原理计算在长余辉发光材料研究中的应用，该基础研究工作对新型长余辉发光材料的探索和学术皆有意义。

本课题以双岛状焦硅酸盐Sr2MgSi2O7:Eu2+, Dy3+为研究对象，利用第一性原理计算方法研究了基质的晶体结构和电子结构、发光中心离子的局域能级、各种本征缺陷及共掺激活剂离子的陷阱形态、陷阱对材料的长余辉发光性能的调控。研究表明，基质中的桥接氧空位和硅反位(Si替代Mg位)在导带底以下1 eV能量范围内形成与连续分布的空能级，它们是电子陷阱的主要来源。金属空位起着稳定电子陷阱的作用。Dy3+离子在费米能级附近引入电子部分填充的杂质能级，该杂质能级的空态形成能量分布较宽（~2 eV）的电子陷阱能级，而满态则通过空态与导带相连，从而揭示了共掺Dy3+离子能够有效延长余晖寿命、提高发光强度的原因。通过比较与Sr2MgSi2O7在晶体结构和能带结构上的差异，本课题从桥接氧空位形成的难易和导带的局域性预测了潜在长余辉发光材料La3GaGe5O16并非是一种高效的长余辉发光材料，与实验相吻合。此外，作为具有快离子性能的长余晖发光材料在锂、钠离子电池材料中的潜在应用，本课题还在锂离子电池材料研究领域也做了一些积累。