通过上转换激发实现高效长余辉发光的设计和光谱学研究

It is generally accepted in theory that high-energy ultraviolet light is necessary in order to effectively charge the traps in persistent phosphors. However, the need of high-energy excitation compromises some emerging applications where the ultraviolet excitation is unsuitable. Therefore, search for effective low-energy excitation approaches (e.g., visible light excitation) is urgently needed, which was identified as a grand challenge in the field. In this proposal, by combining the features of up-converting excited-state absorption and persistent luminescence, we design a new up-conversion charging (UCC) process. In our UCC concept, under an intense low-energy excitation by an appropriate visible-light laser diode, the high-energy electron traps in the Cr3+, Mn2+, Pr3+, Tb3+-activated phosphors can be effectively filled by successive absorption of two visible photons. The persistent luminescence produced by the UCC process is as effective as that excited by the conventional ultraviolet lamp. For further understanding the entire UCC process, we plan to pursue the following three correlated research objectives: (1) investigating the UCC excitation spectroscopy through the optimum combinations of excitation wavelengths and excitation intensities; (2) investigating the electron transfer in the UCC process through thermoluminescence spectroscopy technique; (3) understanding the electronic structures of UCC materials to develop novel UCC persistent phosphors. We believe that the discovery of the UCC phenomenon can potentially revolutionize the ways we study and utilize persistent luminescence.

如何在低能可见光的激发下实现高能陷阱的填充是长余辉材料研究面临的重要挑战。本项目中，申请人结合激发态上转换吸收和长余辉过程，提出“上转换激发的陷阱填充”（UCC）这一新型余辉设计。拟采用高密度的低能激发光源（例如可见光激光二极管）对Cr3+、Mn2+、Pr3+、Tb3+等掺杂材料的余辉陷阱进行有效地填充；进而实现能与紫外灯辐照余辉效果相比拟的UCC余辉发射强度。为了更好地认识和理解UCC现象，本项目将围绕以下三方面开展：(1)优化激发波长和激发功率等参数，发展UCC激发谱学；(2)通过改进的热释光谱学测量，研究UCC的电子传递等物理过程；(3)理解UCC材料的电子结构特点，设计和开发新的UCC材料体系。申请人相信UCC概念的提出能够为长余辉的基础研究和实际应用提供新的视野。

以解决长余辉材料的激发波长限制为目的，本项目工作提出了“上转换激发的陷阱填充”（UCC）这一新型余辉概念，并通过光谱学手段对其激发、电子传递及发射过程进行了系统的研究。.具体取得的学术成果如下：(1) 开发了UCC激发谱学技术，将充能光源由相干激光扩展至生活中常见的发光二极管和白光手电等；(2) 深入研究了UCC过程中电子传递动力学，揭示了充能辐照剂量对陷阱态布居的”读出/写入”动态影响；(3) 扩展了UCC材料体系，在Pr3+、Tb3+、Mn2+、Cr3+ 等掺杂材料体系中实现了从紫外到红外多重谱段的余辉发射。除了计划的科研内容，考虑到项目执行期间爆发的新冠疫情以及紫外光对传播病毒的杀毒功能，申请人在UCC研究的基础上提出并开发了上转换基紫外光源的概念和白昼余辉的概念。.在本项目课题的支持下，主要的产出成果以论文的形式发表于《物理学报》和《Physical Review Applied》等国内外学术期刊。具体的产出成果包括：12篇学术论文，2章书籍章节，2次国际学术会议邀请报告和1项发明专利。人才培养方面，在项目期间，培养毕业了1名博士生和6名硕士生。.总的来说，本项目工作完成了申请书中制定的所有指标。从学术的角度看，项目工作提出的UCC 概念及其动力学研究为长余辉的研究提供了新的视野和技术手段。对申请人来说，项目的支持为其科研工作提供了基本的经费保障，帮助其进行深入的学术探索及科研合作。在此，由衷感谢基金委的资助。

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