Regulation Of Luminescence And Temperature Sensing Properties Of Er³⁺ Doped Phosphors

In recent years,optical temperature sensing based on upconversion of rare earth ions doped materials has attracted much attention in the fields of microelectronics,integrated photonics and biomedicine.How to further improve luminescence and the optical temperature sensitivity of rare earth ions has become the focus of present research.In this thesis,different methods for regulating the luminescence and optical teperature properties of rare earth doped phosphors were systematically studied by changing the matrix type,doping concentration,excitation power and growing quantum dots.The specific research contents of this paper are as follows:The first chapter,the introduction part introduces the research status of rare earth doped phosphors,photoluminescence mechanism,the mechanism of optical temperature sensing and its regulation methods.The second chapter,A method to modify the spectra and optical temperature behaviors of Er³⁺doped Sr₂CaWO₆ phosphors through doping La³⁺,Y³⁺,and Al³⁺ions is reported.The thermometric parameters such as fluorescence emission intensity,fluorescence intensity ratio of red to green emissions,emission intensity ratios of thermally coupled levels(²H_11/2/⁴S_3/2),and temperature sensitivity can be effectively controlled by doping with La³⁺,Y³⁺,and Al³⁺ions into Er³⁺doped Sr₂CaWO₆.Moreover,the optical temperature sensitivity is proved to be dependent on the pump power of 980 nm laser.The third chapter,a facile physical approach is reported to realize cooperative absorption and conversion of dual-band infrared light from Er³⁺doped NaGdF₄ glass ceramics by employing dual-mode excitation source?980 nm+1545 nm?.A synergistic effect of infrared photons induced by dual-wavelength infrared excitation is observed.The dual-mode excited red emission intensity is 2.76times the total red emission intensities from 980 nm and 1545 nm single excitation.This upconversion synergistic effect can be modulated by adjusting excitation power,and is proved to be originated from ground and excited state absorption,in which the Er³⁺ions in metastable states excited by 980 nm?or1545 nm?photons are excited again by the 1545 nm?or 980 nm?infrared photons.A rate equation model is established to simulate the dynamic process in dual-mode infrared upconversion process.The fourth chapter,a new method is proposed to improve the optical temperature sensitivity of Yb³⁺-Er³⁺co-doped CaWO₄ phosphors by doping and controlling excitation powers.It is found that the thermometric parameters such as upconversion emission intensity,intensity ratio of green-to-red emission,fluorescence color,emission intensity ratios of thermally coupled levels(²H_11/2/⁴S_3/2),and relative and absolute temperature sensitivity can be effectively controlled by doping with Li⁺,Sr²⁺,and Mg²⁺ions in the Yb³⁺-Er³⁺co-doped CaWO₄ system.Moreover,the relative sensitivity S_R and the absolute sensitivity S_A are proved to be dependent on the pump power of 980 nm laser.The fifth chapter,it is proposed to regulate luminescence and temperature sensing properties of Er³⁺doped silicate glass by using narrow-bandgap semiconductor quantum dots.The growth of PbS quantum dots in the silicate glass matrix realizes the energy transfer between Er³⁺ions and the PbS quantum dots,realizing the enhancement of upconversion green and red emission.By controlling the growth of the morphology and size of PbS quantum dots in rare earth silicate glass,it is possible to effectively control the optical temperature parameters such as the fluorescence emission intensity,the emission intensity ratio of the thermally coupled energy level(²H_11/2/⁴S_3/2),and the optical temperature sensitivity.This work provides an effective research method for exploring broadband infrared upconversion.