Synthesis And The Study On Photoelectricity Properties Of Perovskite K_mZnF_n(m=1,2;n=3,4) And NaBiF₄ Materials

Lanthanide ion(Ln³⁺)-doped fluoride upconversion luminescent materials can convert low-energy long-wavelength light into high-energy short-wavelength light,and considered to be a more efficient candidate material among materials excited by near-infrared light(NIR).Due to its high electronegativity,low phonon energy,low toxicity,strong ability to penetrate tissue cells,and strong resistance to photobleaching,Ln³⁺doped fluoride upconversion luminescent materials are widely used in solar cells,photothermal diagnosis and treatment,biological imaging,biological probes and other fields.Therefore,the development of rare earth-doped fluoride host materials with excellent optoelectronic properties is promising.In this paper,KZnF₃,K₂ZnF₄ and NaBiF₄ crystals were synthesized in OA/HA and HAc/Et systems by changing reaction temperature,reaction time,solvent ratio,amount of solute substance and concentration of solution.KZnF₃ and K₂ZnF₄host materials were characterized by means of X-ray powder diffractometer(XRD)transmission electron microscope(TEM)scanning electron microscope(SEM)ultraviolet visible spectrophotometer(UV-Vis)and other measuring methods were used,K_mZnF_n(m=1,2;n=3,4):Yb³⁺,Er³⁺/Ho³⁺/Tm³⁺optimal rare-earth activator ion doping ratio simultaneously achieved multicolor output.In addition,K_mZnF_n(m=1,2;n=3,4):Ce³⁺,Co³⁺,Ni³⁺linear sweep voltammetry(LSV),cyclic voltammetry(CV),alternating current impedance(EIS)and time-current(i-t)were used for electrochemical characterization and gradually optimized;NaBiF₄:Yb³⁺,Er³⁺/Tm³⁺was synthesized by using HAc/Et as the reaction solvent,which is cheap and friendly to the environment.The optimal doping concentration of NaBiF₄:Yb³⁺,Er³⁺/Tm³⁺was investigated by fluorescence spectrophotometer under the excitation of 980 nm laser diode.Based on the above research process,the specific results are as follows:(1)In OA/HA solvent system,a series of cubic phase KZnF₃perovskite materials were synthesized by solvothermal method,which is easy to operate,under different reaction temperature,reaction time and solvent ratio conditions.The experimental data showed that when the ratio of OA to HA was 3/1,the reaction temperature was 240?,and the reaction time was 10 d,the sample of KZnF₃ was uniform in appearance and had good crystallinity.The lamellar structure and size were observed by SEM and TEM.At the same time,under the excitation of 980 nm laser diode,the fluorescence spectrophotometer was used to investigate the optimal concentration of KZnF₃:Yb³⁺,Er³⁺/Ho³⁺/Tm³⁺ions.When the concentration of Er³⁺,Ho³⁺and Tm³⁺ions were 3%,3%and 0.5%,respectively,the sample luminescence was the strongest.The electrochemical properties of LSV,CV,EIS and i-t were optimized by doping Ce³⁺,Co³⁺and Ni³⁺.Finally,the over-potential of KZnF₃:30%Co³⁺sample over-potential was reduced to 270 m V,and the AC impendengce was reduced to within 50?.(2)The hexagonal phase K₂ZnF₄ perovskite material was prepared by solvothermal method with high efficiency and safety in OA/HA solvent system by changing reaction temperature and solvent ratio.The experimental data show that when the ratio of OA/HA is 3/1 and the reaction temperature is 180?and the reaction time is 48 h,the pure phase K₂ZnF₄ crystal with good crystallinity is synthesized.On this basis,the optimal doping ratio of Yb³⁺/Er³⁺,Yb³⁺/Ho³⁺and Yb³⁺/Tm³⁺co-doped K₂ZnF₄ was adjusted,and the electrochemical LSV,CV,EIS and i-t properties of the sample were characterized and analyzed by doping Ce³⁺,Co³⁺and Ni³⁺.When K₂ZnF₄:30%Co³⁺,the sample had good electrochemical performance,the over-potential value was 270 m V and the impedance was reduced to less than 25?.(3)In the system of glacial acetic acid(HAc)and ethanol(Et),the hexagonal NaBiF₄fluoride matrix was synthesized by sol-gel method at room temperature by changing the reaction time,the amount of solute,the ratio of solvent,the concentration of solution,etc.The experimental data showed that the pure phase NaBiF₄was obtained when the reaction conditions were 0 min,5 NH₄F,0.5 Na OH,5 mol/L HAc,and Et/HAc=2/1 at room temperature.Meanwhile,the optimal doping ratio of Yb³⁺and Er³⁺/Tm³⁺co-doped NaBiF₄ were adjusted to 20%,3%and 0.9%,respectively.