Collaborative Research: Multiphoton Phosphors Based on Vacuum Ultraviolet Excitation

这个实验研究项目的目的是研制多光子荧光粉。这些材料将一个初始的VUV高能光子转化为两个能量较低的可见光子，从而建立一个大于1的量子效率。这里定义的方法是利用镧系离子之间的能量转移过程来实现多光子过程。一个镧系离子吸收紫外光子。接下来是一个交叉松弛的能量转移过程，在这个过程中，最初被激发的离子与另一个离子分享一部分能量。这两个离子都有足够的能量来发射一个可见光子，从而有效地利用来自灯放电的VUV光子来产生两个可见光子。本文将研究三种涉及4fn和4fn-15d结构的镧系离子的能量转移方案。根据有关镧系元素的能级及其对宿主物质的依赖的文献数据，选择了一些离子对和合适的宿主进行研究，将最大限度地提高成功的机会。由于这些方案涉及使用位于导带边缘附近的固体的高激发态，在那里可能发生局域和非局域状态的混合，并且光电离和电荷转移过程可能使问题复杂化，因此有必要从物理和材料的角度解决有关这些高激发态的性质和动力学的一些基本问题。该项目将由三个小组合作进行。乔治亚大学的物理小组将对荧光粉进行光学表征，并研究其高激发态的动力学特性。俄勒冈州立大学的化学小组将生产所需的荧光粉并优化其性能，他们还将开发可能具有所需性能的新组合物。欧司朗Sylvania的科学家将为该项目贡献他们的时间，为荧光粉的开发和评估提供实验和理论支持，特别是关于它们在实际照明设备中的实际用途。美国利用其电力能源预算的近25%来满足我们社会的照明需求。目前的荧光灯的插电效率约为30%，它们的废弃导致大量汞排放到环境中。拟议的研究将提供必要的工艺和材料，使飞跃到一个新的多光子荧光粉技术和一种新的高效率照明形式，这将导致能源消耗的大幅减少，并消除照明中的汞。该项目将涉及三个小组之间的合作；佐治亚大学的物理学家，俄勒冈州立大学的化学家，以及欧司朗公司的工业科学家。学生将深入了解多光子工艺和材料设计，为未来在照明行业或学术界的贡献奠定基础。

This program of experimental research is directed to the development of multiphoton phosphors. These materials convert an initial VUV high-energy photon into two visible photons of lower energy, thereby establishing a quantum of efficiency that can be greater than one. The approach defined here is to use energy-transfer processes among lanthanide ions to implement the multiphoton process. One lanthanide ion absorbs the VUV photon. This is followed by a cross-relaxation energy-transfer process in which the initially excited ion shares a portion of its energy with a different ion. Both ions are left with enough energy to each emit a visible photon of light, thereby efficiently utilizing the VUV photon from the lamp discharge to produce two visible photons. Three schemes will be examined for the energy transfer that involve both the 4fn and the 4fn-15d configurations of the lanthanide ions. From literature data on the energy levels of the lanthanides and their dependence on host material, a number of ion pairs and appropriate hosts have been selected for study that will maximize the chance for success. Since these schemes involve the use of highly excited states of solids located near the edge of the conduction band where mixing of localized and delocalized states can occur and where photoionization and charge-transfer processes can complicate the problem, it will be necessary to address some of the fundamental issues concerning the nature and dynamics of these highly excited states from the physics and materials perspectives. The project will be conducted by collaboration among three groups. The physics group at the University of Georgia will perform the optical characterization of the phosphors and study the dynamical properties of their highly excited states. The chemistry group at Oregon State University will produce the required phosphors and optimize their properties, and they will also develop new compositions that are likely to have the desired properties. Scientists at Osram Sylvania will contribute to the project with their time providing both experimental and theoretical support on the development and evaluation of phosphors, especially regarding their practical usefulness in real lamp devices.The U.S. utilizes almost 25% of its electricity-energy budget to satisfy the lighting requirements of our society. Current fluorescent lamps have a wall-plug efficiency of about 30% and their discard results in the dumping of large amounts of mercury into the environment. The proposed research will provide much needed insight into the processes and materials that are necessary to make the leap to a new multiphoton-phosphor technology and a new form of high-efficiency lighting that will lead to a substantial reduction of energy consumption and the elimination of mercury in lighting. The project will involve collaboration among three groups; physicists at the University of Georgia, chemists at Oregon State University, and industrial scientists at Osram Sylvania. Students will develop an in-depth understanding of multiphoton processes and materials design, providing a base for future contributions in the lighting industry or academe.