First-principles Study Of The Spectral Parameters Of Rare Earth Ions

With the development of computer configurations and the theoretical calculation methods, the first-principles calculation get more and more attention, and have been widely used in the rare earth-doped luminescent material.The research content of this dissertation is consisted of four chapters. The first chapter is a general introduction to the electronic structures of rare earth ions, the specific applications of rare earth-doped luminescent materials, and the main work of this dissertation.In chapter2, we introduce the theory of first-principles calculation and density functional theory (DFT) at first. Then, we investigate the local coordination structures, the4f and5d energy-level structures, and the spectral parameters of Ce3+ion in garnet phosphors with the combination of the first-principles calculations and the phenomenological approaches.The main research works of this dissertation are described and discussed in chapter three. Ce3+-doped garnet phosphors are important for producing white light-emitting diode (LED) owing to their high conversion efficiency, good stability and high color-rendering index. The researchers can tune the emission colors of phosphors and generate high-quality white light by means of co-doping Ce3+ion and other impurities in garnet phosphors. Charge compensation and energy transfer mechanisms are critical questions prevalent in Ce3+-doped garnet phosphors (even in the general rare-earth luminescent materials). On the basis of the different types of charge compensation, the modification in the local coordination environments around Ce3+ions and the tuning of the emissions of the5dâ†'4f transitions can be achieved. Moreover, the energy transfer between different types of luminescence centers plays a key role, especially when the characteristic transitions of one type of luminescence centers are difficult to pump. In this research project, we will investigate the Ce3+-doped garnet phosphors via the first-principles approaches:1) studying the effects of the different types of charge compensation on the luminescence process, the energy levels and transitions of luminescence centers, and the luminescence properties of phosphors;2) analyzing and validating the energy transfer process between the different types of luminescence centers from the microscopic view;3) designing novel Ce3+-doped phosphors for white LED and subsequently carrying out theoretical calculations and validations. It is expected that the outcome of this research would provide theoretical support and guidance for the synthesis of the novel phosphors and the achievement of the white LED with more outstanding properties.In chapter4, we introduce our calculation on vanadate...