Optical Properties Research Of Metal Halide Perovskite Materials And Their Application In Anti-counterfeiting

Low imitation and high concealment are the main goals of packaging anti-counterfeiting materials,while optical anti-counterfeiting materials are commonly used in the field of packaging anti-counterfeiting due to their simple production.Metal halide perovskite has attracted a lot of attention because it is well suited for application in optical anti-counterfeiting and has many advantages over other materials,including inexpensive synthesis costs,flexible emission wavelengths,high luminescence efficiency,and convenience to be transformed into ink.It is still a difficult problem to create perovskite anti-counterfeiting materials with single-component,multimodal fluorescence,and high stability.In order to realize their applications in the field of high-level packaging anti-counterfeiting,we modify the multimodal luminescence properties and enhance the photothermal stability of the materials in this study in the following aspects:（1）Zr⁴⁺/Bi³⁺codoped Cs₂Ag_0.3Na_0.7InCl₆downconversion bimodal light-emitting anti-counterfeiting materials were prepared and their luminescence mechanisms were investigated.The results of spectral analysis reveal that the[ZrCl₆]^2-octahedral characteristic emission contributes to the blue luminescence in the dual-doped sample under UV 254 nm excitation,while the self-trapped exciton（STE）luminescence of the Cs₂Ag_0.3Na_0.7InCl₆:3%Bi³⁺matrix material contributes to the yellow luminescence.Both emission intensity ratios exhibit a clear dependence on Zr⁴⁺.By varying the Zr⁴⁺concentration,it is possible to produce a dual-band tunable emission that spans the entire visible spectrum.However,under UV 365 nm irradiation,samples with varying Zr⁴⁺doping concentrations only exhibit exhibit only yellow STE emission from the matrix material.The Zr⁴⁺/Bi³⁺codoped Cs₂Ag_0.3Na_0.7InCl₆material shows promising applications in the field of optical anti-counterfeiting and has been used to produce a variety of dual-modal luminescence anti-counterfeiting patterns based on the above luminescent properties.（2）Trimodal luminescent materials with good optical properties were created by doping Cs₂ZrCl₆with Sb³⁺to increase the level of anti-counterfeiting.Under UV 254nm irradiation,the as-prepared materials show blue STE emission from[ZrCl₆]^2-octahedra.Warm white light is obtained by the sample under UV 310 nm illumination,which contains the blue band corresponding to the ¹P₁→¹S₀transition（400-550 nm）and the red band corresponding to the ³P₁→¹S₀transition（550-720 nm）from Sb³⁺.The luminescence of the sample is mostly produced by the red band associated with the Sb³⁺³P₁→¹S₀transition under UV 365 nm irradiation.Accordingly,under UV irradiation at 254,310,and 365 nm,the anti-counterfeit patterns developed by Sb³⁺-doped Cs₂ZrCl₆exhibit blue,warm white,and red trimodal luminescence,respectively.（3）By combining upconversion and downconversion luminescence,we developed the Yb³⁺/Eu³⁺/Ho³⁺codoped Cs₂Ag_0.3Na_0.7InCl₆material system to provide single-component multimodal luminescent anti-counterfeiting materials with higher levels of anti-counterfeiting properties.The sample displayed yellow luminescence from the STE of Cs₂Ag_0.3Na_0.7InCl₆matrix material under UV 300 nm excitation,red characteristic luminescence from Eu³⁺ions under UV 394 nm excitation,and green luminescence from the Ho³⁺⁵F₄→⁵I₈transition sensitilized by Yb³⁺under NIR 980nm excitation.The material systems described above are designed to combine upconversion and downconversion luminescence in a single-component material.They also have multimode anti-counterfeiting properties that depend on various excitations,which significantly raises the material’s optical anti-counterfeiting level.（4）Because of the added complexity of decryption,near-infrared luminescence anti-counterfeiting materials are more concealable.Based on this,we created a trimodal Yb³⁺/Er³⁺co-doped Cs₂NaHoCl₆anti-counterfeiting material that emits light in the visible and near-infrared regions.The single component material has both visible and near-infrared emission,and under 980 nm laser excitation,the visible region exhibits characteristic green upconversion luminescence from Ho³⁺and Er³⁺,while in the near-infrared region,it contains characteristic emission from Er³⁺ions.Under UV 380 nm excitation,Yb³⁺/Ho³⁺/Er³⁺superimposed converted luminescence was produced in the near-infrared region.In the field of package anti-counterfeiting,this complexity of multimode encryption and decryption has a wide range of application potential and stronger anti-counterfeiting concealment and security levels.（5）An important development path to raise the level of anti-counterfeiting is photoluminescent capped with thermochromic multiple anti-counterfeiting.We selected the MAPbBr₃material system that is sensitive to temperature response.The prepared anti-counterfeiting patterns we created changed from yellow-green in natural light to pure green when exposed to UV 365 nm radiation.They also displayed a strong temperature dependence before and after heating at temperatures above 45°C,and a significant color-changing effect could be seen with good reversibility and consistency.The luminescence and hydrothermal stability of the organic-inorganic hybrid perovskite were significantly improved by the addition of 3,3-diphenylpropylamine（DPPA）and n-octylamine bromide（OABr）biligands and polymer encapsulation,and the tolerance of the materials under harsher transport and storage environments was improved.