Research On The Optical Properties Of Novel Defective Luminescent Glasses And Tunable White LEDs

The white LED based on luminescent glass possesses many advantages,such as environmental friendliness,processing convenience,long service life,unlimited specifications and so on,which can achieve the huge challenges to white light source in various fields.Therefore,the white light emission with high quality in luminescent glass has been gradually become a research hotspot in recent years.Traditional white luminescent glass achieves the white light emission by doping with multiple activators in glass matrix,which not only increases the industrial cost of white LED device,but also increases the difficulty of tunable white luminescent emission.This dissertation mainly researches on the optical properties of two glass matrixes with luminescent defect centers and tunable white light performance of single-doped rare earth/transition metal ions glasses,as well as explores the assembled LED design and the photoelectric response characteristic,which provide theoretical and experimental basis for the application of these two defective glass materials on white LEDs.The dissertation includes the following six chapters.The first chapter is the literature review.It mainly introduces the concept and principle of luminescent glass for white LEDs.And the types and luminescent mechanisms of common glass matrixes and visible light emission activators are briefly summarized.Subsequently,it mianly introduces two kinds of glass matrixes with luminescent defect activator—tin-containing glass and binary phosphate oxynitride glass,including their optical spectroscopic properties,luminescence mechanisms,and defect structure analysis,which put forward the main research contents in this paper.The second chapter is the experimental and theoretical calculation.It mainly introduces the chemical composition and sample preparation of the two glasses,the main performance tests and the corresponding experimental test instrument information.Furthermore,it lists the calculation or definition formulas of the physical parameters involved in this paper.The third chapter is the research on the optical properties and structure of tin fluorophosphate glass.It mainly researches the dynamic spectroscopy characteristics,related defect structures and the energy relaxation mechanism of Sn²⁺centers in the glass matrix.The coexistence of fluorescence and phosphorescence phenomenon and the photoelectric response characteristics are reported for the first time in tin fluorophosphate glass.The results show that the increase of the phosphate component can improve the energy transfer efficiency of the Sn²⁺by affecting the S₁/S₁’→T₁transition.In addition,it is demonstrated that the oxygen vacancy defect around the Sn atom can capture electrons under light excitation and transform into F⁺like defect.Taking it as an electron energy trap,the double relaxation emission of T₁→S₀in the Sn²⁺activator is achieved.This brand-new energy transfer mechanism can explain the coexistence of fluorescence and phosphorescence and the photoelectric response characteristic in tin fluorophosphate glass.The fourth chapter is the research on the tunable white light emission in the rare earth element doped tin fluorophosphate glass.The optical properties and energy transfer mechanism of Eu³⁺ion in tin fluorophosphate glass are mainly investigated.And the tunable white light emission is achieved in this glass.At the same time,a white LED scheme with excellent performances can be obtained by adjusting the glass matrix components.The results show that the glass presences an energy transfer process between the Sn²⁺activator and Eu³⁺ion during their intrinsic luminescence.It makes the Eu³⁺doped tin fluorophosphate glass have higher the luminescent efficiency when the doping concentration of Eu³⁺ions increases.At the same time,the tunable white light emission in this glass can be achieved by changing the excitation wavelength.Under the excitation of a 375 nm chip,a self-assembled white light LED exhibits warm white light emission with a low color temperature.And under the excitation of a 390 nm chip,it is a cold white light LED with a high color temperature.In addition,by increasing the proportion of the phosphate component,white light emission with the highest quantum efficiency is obtained in the cold white light LED device based on TFP641Eu5 sample,and its white light characteristics are shown as:CIE=（0.31,0.300）,Ra=92.3,the absolute quantum efficiency=12.81 and the color temperature=8769 K.The fifth chapter is the research on the optical properties and tunable white light emission of the transition element doped binary phosphate oxynitride glass.It mainly introduces the valence state and optical properties of Mn ions in zinc phosphate oxynitride glass,as well as the tunable white light properties of this glass in LED.Mn³⁺ion is proposed for the first time as"energy harvesting probes",and the energy transfer law of Mn²⁺ions with mixed valence states is analyzed by static spectroscopy.The results show that Mn ions remain in a higher reduced state in the zinc phosphate nitroxide glass,which exhibits the higher Mn²⁺ion concentration than that in the traditional zinc phosphate glass matrix.It enhances the ion-ion exchange coupling of Mn ions,and the Mn ions doped zinc phosphate nitroxide glass shows stronger red emission.Due to this energy transfer between the Mn ion and the nitrogen-phosphor electron-hole defect activator in this glass,its self-assembled WLED shows a tunable warm white light emission under the excitation of the UV chip,whose white light characteristics are shown as:CIE value=（0.33,0.35）,color temperature=5228 K,color rendering index Ra=86.The sixth chapter is the conclusion of the dissertation,in which the content and results of the full text work are summarized,and points out the shortcomings in the work and the outlook for future work.