Study On The Tunable Luminescence Of NaYF₄:Er³⁺and The Photoelectric Energy Transfer Mechanism Of NaYF₄:Er³⁺,Cu²⁺

Up-conversion luminescence of rare earth has always been a research hot topic in the field of photoluminescence,and it has been widely used in the fields of biological imaging,three-dimensional display,photovoltaic industry and so on.However,the research on rare earth upconversion is still less concerned in two aspects at present:first,up-conversion of rare earth mainly uses 980 nm laser as the light source,and other single-wavelength lasers such as 1550 nm and dual-wavelength lasers such as 980 nm+1550 nm are rarely studied as excitation light sources;second,a lot of work has been done to study the doping of heterogeneous metal ions to improve the luminescence efficiency of up-conversion.However,few studies have been done to optimize the photoelectric properties of up-conversion through metal ion doping,and there is also a lack of in-depth research on the photoelectric energy transfer mechanism of up-conversion materials.In this paper,the NaYF₄:xEr³⁺?x=0%?3%?5%?7%?9%mmol?up-conversion crystallites were prepared by hydrothermal method.The phase and morphology of NaYF₄:xEr³⁺crystallites were analyzed by X-ray powder diffraction method and field emission scanning electron microscope.The up-conversion emission spectra of NaYF₄:xEr³⁺crystallites were tested by using a fluorescence spectrometer under1550 nm excitation conditions,980 nm excitation conditions and 980 nm+1550 nm dual-frequency excitation conditions,in which NaYF₄:5%Er³⁺has the strongest up-conversion luminescence,and under different excitation light conditions,the up-conversion luminescence colors of NaYF₄:5%Er³⁺crystallite are different,which makes NaYF₄:5%Er³⁺crystallites a candidate material in the field of multicolor display.The effects of hydrothermal reaction conditions on the phase,morphology and luminescence properties of NaYF₄:5%Er³⁺crystallites were studied.NaYF₄:5%Er³⁺,yCu²⁺?y=0%?2%?5%?10%?20%mmol?crystallites were synthesized by doping metal Cu²⁺ions.The electro-optical performances of NaYF₄:5%Er³⁺,yCu²⁺was tested with an electrochemical workstation.The test results show that when the Cu²⁺ion content is 10%mmol,the crystallite has the highest light current and the weakest up-conversion luminescence.Based on conservation of energy,the photoelectric energy transfer mechanism of NaYF₄:5%Er³⁺,10%Cu²⁺is discussed.The photoelectric properties of the three materialsNaYF₄:5%Er³⁺,10%Ca²⁺?NaYF₄:5%Er³⁺,10%Mg²⁺and NaYF₄:5%Er³⁺,10%Cu²⁺were compared under the same conditions.So the impedance of NaYF₄:5%Er³⁺,10%Cu²⁺is the minimum,the light current is the maximum,and the photoelectric performance is excellent.This work used Cu²⁺ion doping strategy to synthesize up-conversion photoelectric materials.Promoting the conversion of light energy into electrical energy in up-conversion materials,a new energy transfer mechanism for up-conversion photoelectric materials is proposed,NaYF₄:5%Er³⁺,10%Cu²⁺are candidates for photoelectric sensors.The main research contents of this paper are as follows:1?Hexagonal prism NaYF₄:xEr³⁺up-conversion crystallites were synthesized by hydrothermal method,with uniform crystal size and good dispersion.Under the excitation condition of 1550 nm,the effects of Er³⁺ion doping content on the up-conversion luminous efficiency were explored.When the Er³⁺ion doping content is 5%mmol,NaYF₄:xEr³⁺up-conversion crystallites have the highest up conversion efficiency.The up-conversion enhancement mechanism is discussed.A dual-frequency laser device was designed,and the up-conversion emission spectra were compared dunder 1550 nm excitation conditions,980 nm excitation conditions and 980 nm+1550 nm dual-frequency excitation conditions.Through the CIE chromaticity diagram,the difference of the emitted light color under different excitation conditions was analyzed,and the tunable multi-color emission of NaYF₄:5%Er³⁺up-conversion crystallite was realized,and the corresponding luminescence mechanism was explained.2?The NaYF₄:5%Er³⁺crystallite with the strongest conversion luminescence was taken as an example,under 1550 nm excitation conditions,the effects of fluoride ion source,hydrothermal temperature,amount of fluoride ion,pH value of precursor solution,ligand and the order of addition of precursor solution on the phase,morphology and luminescence properties of microcrystals in hydrothermal reaction were studied.The possible growth mechanism of crystals under different reaction conditions and the reasons affecting the up-conversion efficiency were explained.3?Synthetic NaYF₄:5%Er³⁺,yCu²⁺?y=0%?2%?5%?10%?20%mmol?crystallites,which used an electrochemical workstation to test its impedance and light current under 1550 nm excitation conditions,the effects of Cu²⁺ion doping content on the photoelectric properties of materials were discussed.According to the up-conversion emission spectrum,thermal effect test and conservation of energy,a new up-conversion photoelectric energy transfer mechanism is proposed.The photoelectric properties of three materials NaYF₄:5%Er³⁺,10%Ca²⁺?NaYF₄:5%Er³⁺,10%Mg²⁺and NaYF₄:5%Er³⁺,10%Cu²⁺were compared under the same conditions.The experimental results show that NaYF₄:5%Er³⁺,10%Cu²⁺has the minimum impedance and the maximum light current,and has more excellent photoelectric properties.