The Upconversion Luminescence Regulation And Photoelectric Function Research Of Rare Earth Doped Molybdate Materials

The object of this dissertation is upconverison materials with different rare earth ions doped molybdate matrix.Based on the method of combining the theoretical calculation and experiment progress,we explored the upconversion luminescence performance of these materials under different excitation source and low temperature regulation,and developed the application in LED,temperature sensing,dual-mode anti-counterfeiting and logic gate optical functional fields.The influence mechanism of doping ions on the structure and properties of molybdate matrix upconversion luminescence material was also discussed,and the upconversion mechanisms of fluorescence enhancement and temperature regulation were revealed.The main work was as follows:The lattice structure,electronic and optical properties of KLa（Mo O₄）₂ and KLa（Mo O₄）₂:Re³⁺(Er³⁺,Yb³⁺/Er³⁺)systems were calculated by first-principles method.After doping rare earth ions,the cubic phase structure of the system didn’t change,and the crystal cell volume decreased.A new peak appears at Fermi level and the gap width was reduced,which was favorable for electron transition.Compared with undoped and single-doped systems,dual-doped system had the highest absorption rate and lowest reflectivity in the infrared band,which was conducive to upconversion luminescence.KLa（Mo O₄）₂:15%Yb³⁺/2%Er³⁺sample was prepared by high temperature solid state method,and the emission peaks at 532 nm,555 nm and 672 nm were observed under the excitation of 808 nm,980 nm,1064 nm,1470 nm or 1550 nm wavelength.Utilizing the upconversion luminescence characteristics of KLa（Mo O₄）₂:15%Yb³⁺/2%Er³⁺,this phosphor was combined with the near-infrared chip on the market,and the green light LED device was successfully constructed.It was found that the fluorescence enhancement of KLa（Mo O₄）₂:15%Yb³⁺/2%Er³⁺was achieved at co-excitation of 980 nm and 1550 nm dual wavelength.When the excitation power of 980 nm and 1550 nm are 56.2 m W and 343 m W,the enhancement effect of green and red light was the most significant,and the enhancement factor was1.21 and 2.03,respectively.The temperature sensitivity of KLa（Mo O₄）₂:15%Yb³⁺/2%Er³⁺has been studied based on thermal-coupled energy levels of Er³⁺(²H_11/2,⁴S_3/2)in the range of 120 K to 300 K.The absolute and relative sensitivity of KLa（Mo O₄）₂:15%Yb³⁺/2%Er³⁺reached the maximum at 300 K and 120 K,respectively,which were 0.0047 K^-1 and 5.8%K^-1,respectively,indicating that this material could be applied in the field of low temperature sensing.Under the excitation of 980 nm wavelength,the electron transition process of Ho³⁺and Yb³⁺co-doped KLa（Mo O₄）₂ materials could be controlled by thermal manipulation and multicolor upconversion luminescence was achieved.At low temperature envrionment,the luminescence color of this material changed from bright green to dark yellow when the temperature was increased from 85 K to 240 K.Based on the fluorescence intensity ratio technology of the non-thermal coupling energy level of Ho³⁺,this material exhibited excellent temperature sensing performance in the low temperature region,and its absolute and relative sensitivity reached the maximum value at 85 K,which were 0.049 K^-1 and4.6%K^-1,respectively.Based on the thermochromic luminescence properties of KLa（Mo O₄）₂:Yb³⁺/Ho³⁺upconversion material and its high sensitivity to low temperature,KLa（Mo O₄）₂:Yb³⁺/Ho³⁺upconversion fluorescent safety ink and upconversion photon barcode were developed,which realized a novel dual-mode anti-counterfeiting method by visual reading and digital recognition.By using 1470 nm and 1550 nm dual wavelengths as trigger signals,Gd₂（Mo O₄）₃:Yb³⁺/Er³⁺could be achieved significant fluorescence enhancement and color regulation.Furthermore,an upconversion logic gate system was formed to perform multiple combinational logic operations.When the excitation power of 1470 nm and 1550 nm lasers are 266 m W and 433 m W,the fluorescence enhancement effect of dual-wavelength excitation is optimal,and the enhancement factor of green and red light is 2.06 and 1.6,respectively.Combined with the influence of excitation power and low temperature on dual-wavelength enhancement,1470 nm and 1550 nm excitation sources were used as input signals,and the changes of green or red light relative emission intensity and red/green intensity ratio signal of this material were monitored,an upconversion logic system was developed to perform double-output（YES+OR,AND+XOR,AND+INHIBIT,YES+INHIBIT）and three-output（AND+YES+OR）.It was worth noting that multiple output signals of the upconversion emission system can perform different logic operations at the same time,which expands the capacity of the logical information base and improves the capability of information processing.