Preparation And Application Exploration Of Several Rare Earth Halogenated Perovskite And Fluoride Luminescent Materials

Recently,metal halide perovskite materials have played an important role in LED lasers,photodetectors and other photoelectric applications due to their excellent properties,such as high defect tolerance,optical tunability,photoelectrinic properties large absorption coefficient and others.However,due to the ionic properties of perovskite crystals and the dynamic properties of ligands on the nanocrystals(NCs)surface,the stability of perovskite NCs is poor at room temperature,which affects its optical properties and limits its practical application.Therefore,improving the stability of perovskite plays an important role in its application and development.Due to their rich spectral lines(from ultraviolet to near-infrared),narrow band and linear emission,high luminous color purity and long fluorescence lifetime,the incorporation of rare earth ions is a promising method to control the electronic and optical properties and structural stability of halogenated perovskite NCs.Moreover,rare earth(RE3+)ions doped luminescence nanomaterials can not only observe the down-conversion emission of two or more low-energy photons by one high-energy photon,but also absorb low-energy near-infrared light to produce up-conversion(UC)of high-energy visible light.In addition,RE3+doped UC luminescent materials have attracted much attention due to their excellent properties and wide application potential.In this thesis,perovskite luminescent materials,which are coated with oxide,doped with rare earth ions were synthesized at room temperature or high temperature.And the crystal structure,optical properties,stability and optical applications of perovskite luminescent materials were also studied.In addition,the effects of ion doping on the optical properties of rare earth up-conversion luminescent materials have also been studied.The specific content is summarized as follows:1.The process of conversion from CsPbBr3 to Cs4PbBr6/CsPbBr3 microcrystals(MCs)by a ligand-assisted supersaturated recrystallization(LASR)method has been studied.To improve its stability,CsPbBr3 has been successfully converted into monodisperse Cs4PbBr6/CsPbBr3@Ta2O5 core-shell MCs through a facile one-step sol-gel method at room temperature.And Cs4PbBr6/CsPbBr3@Ta2O5 MCs display great enhancement in photoluminescence quantum yield(PLQY)(up to 94.7%)and photo luminescence lifetime(up to 67.8 ns).Compared with Cs4PbBr6/CsPbBr3,Cs4PbBr6/CsPbBr3@Ta2O5 has better light stability and thermal stability.Furthermore,the luminous efficiency of the WLED device based on Cs4PbBr6/CsPbBr3@Ta2O5(31.9 lm/W)is twice that of the WLED device fabricated by Cs4PbBr6/CsPbBr3(15.2 1m/W)2.We propose an improved hot-injection technique to synthesize a high photoluminescence quantum yield(PLQY)and high stability of CsPbCl3:Yb3+,Mn2+NCs with triple-wavelength emission spanning from visible(VIS)to near-infrared(NIR)regions through co-doping amount of Yb3+and Mn2+ ions.Due to formation of Yb-Mn dimer,it can surprisedly find that no matter the doping concentration of Yb3+or Mn2+increased,the luminescence intensity of the corresponding characteristic luminescence of Yb3+and Mn2+will be enhanced simultaneously.Eespecially for Mn PL emission,the Mn-PLQY reaches 92.3%which is about 50 times that of undoped Yb3+ion.Moreover,compared with high PLQY of CsPb1-xMnxCl3,the CsPbCl3:Yb3+,Mn2+NCs has better light stability and thermal stability.Furthermore,due to the co-doping of Yb3+,the LED luminescence efficiency of 30%Mn based on CsPbCl3:x%Yb3+increased from 0.9 to 8.2 lm/W,and the luminescence efficiency of the WLED device prepared by the mixed coating of prepared CsPbCl3:25%Yb3+,30%Mn2+and green powder CsPbBr3 on 395 nm GaN LED chip reached 20.5 lm/W.3.Yb3+/Ln3+(Er3+ Ho3+,Tm3+)codoped Cs2AgBiCl6 NCs was synthesized by an improved hot-injection method.Due to codoping of Yb3+and Ln2+ ions,it not only endows Cs2AgBiCl6:Yb3+/Ln3+NCs with the characteristic emission of Yb3+or Ln3+ions under UV excitation but also enables the NCs to exhibit UC characteristic emission of Ln3+under 980 nm excitation.What's more,copmared with Cs2AglnCl6 double perovskite(DP),Cs2AgBiCl6 DP as the matric exhibits better UC and down-conversion luminescence performance.Furthermore,because of multi-mode luminescence characteristics of the NCs,it has different potential application prospects under different luminescence models,especially for Cs2AgBiCl6:Yb3+/Er3+.For instance,based on the down-conversion spectral characteristics of Cs2AgBiCl6:Yb3+/Er3+NCs,the phosphor-converted(pc)LED containing visible and NIR region was prepared by combining the prepared sample with 460 nm pc-LED chip.Additionally,by investigating the temperature-dependent UC luminescence properties of Cs2AgBiCl6:Yb3+/Er3+,the NCs have potential for temperature sensing with the maximum thermal sensitivity of 0.0082 K-1 at 423 K4.Ga3+ions doped NaYF4:18%Yb3+/2%Er3+have been prepared through a facile one-pot solvothermal method.UC emission intensity was significantly enhanced by introducing Ga3+ions into the lattice of NaYF4:18%Yb3+/2%Er3+ especially the green UC emission.By doping 25%Ga3+,the green UC emission is increased by 30 times,while the red emission is enhanced by only 8 times.Meanwhile,with Ga3+concentration increasing,the size of the resulting NaYF4:18%Yb3+/2%Er3+/x%Ga3+particles decrease gradually.Therefore,by Ga2+ doping,the morphology of particles and local symmetry around Er3+ions were been changed,resulting in the selective enhancement of green UC emission.In addition,the temperature dependent UCL properties of NaYF4:18%Yb3+/2%Er3+/25%Ga3+and NaYF4:18%Yb3+/2%Er3+were investigated.The maximum thermal sensitivity of NaYF4:18%Yb3+/2%Er3+/25%Ga3+could reach 0.0046 K-1 at 498 K,while that of NaYF4:18%Yb3+/2%Er3+without doping of Ga3+was only 0.0034 K-1.Therefore,NaYF4:18%Yb3+/2%Er3+/25%Ga3+with strong green UCL could be served as a potential candidate for sensitive temperature sensing.